History--Eight Digit US telephone numbers? [telecom]
Lisa or Jeff
Several ads in the NYT in 1947 had HOllis 5-10nnn numbers (HOllis 5-
was in Queens, NY). Old Bell System literature says some large city
exchanges could have as many as 10,500 lines--this was the maximum
jacks within reach of an operator.
I was wondering how common this was in the US (presumably it was in
big cities), and how long it lasted.
Some background:
The Bell System developed the 'panel' dial exchange for big cities.
It was designed to have more capacity and switch more efficiently than
was possible with step-by-step gear; it utilized some basic common
control circuits.
A key feature of panel was compatibility with the many manual
exchanges a switch would connect to. For calls from manual exchanges
to a dial exchange, operators had a keypad to enter the number quickly
(either the originating operator or dedicated "B" operators* for that
function).
For calls from dial users to a manual exchange Bell wanted the
connection to be easy from the subscriber's point of view. Thus, dial
subscribers dialed all their city calls regardless of the type of
exchange they were calling--they did not have to know whether the
called exchange was dial or manual. In this way it was easier to
convert manual exchanges to dial.
To accomplish this, inward operators at manual exchanges had a display
panel indicated the desired number. The display was controlled by the
dial switch, which translated the called number into a signal to light
the appropriate signal lamps.
The literature on this notes that a manual exchange could have up to
10,500 lines (not merely 10,000). The display provided for this by
having a leading fifth digit of 0 or 1. Presumably callers to such an
exchange would dial eight digits.
(The inward operator display also accomodated the party line suffix
letter, but that is beyond the scope of this discussion.)
So, would anyone know if eight digits were actually dialable in New
York City or in other places, as the literature suggests? If so, how
long did it last? I presume as preparations for DDD came along the
eight digit subscribers got new numbers.
Thanks.
*In large cities, manual switching required two operators--an "A" and
"B" operator. The A operator answered the subscribers request. After
the subscriber gave the number "Main 1234", the A operator would plug
into the Main exchange where a "B" operator would take the call. The
A girl passed the "1234" to the B girl, who made the final
connection. Because in big cities most calls were out of the exchange
all calls were handled this way. Early dial automation continued this
pattern of A and B handling.
jsw
>was in Queens, NY).
I know that there's anecdotal evidence that suggests that some
panel offices did indeed have over 10,000 lines. However (comma) ...
Wow {dusting off very rusty memory cells}, I actually knew this
CO back in the years when I was more of a phone 'enthusiast'. ;-)
I'm trying to think back, and IIRC this (465) was panel in the
early 70s, which would imply that it was converted from manual
to dial (panel) prior to WWII. My impression of the age of the
building was that it was definitely pre-war. LOL, I could even
drive you to where it was at the time. ;-) It could have been
a #5 crossbar, making it possible that it was still manual in
1947. I do know that Chicago had some manual service into the
mid 1950s, as did Omaha, home of Ma Bell's first full-scale
panel deployment.
See my final conclusion below ...
I was far more familiar with the Floral Park office, not too
far east of the Hollis office, which was at the time a #5
crossbar, to which I've referred here in the Digest on occasion.
This was unique in that it served both 212 and 516 prefixes at
the time. But back to the subject ...
>So, would anyone know if eight digits were actually dialable in New
>York City or in other places, as the literature suggests? If so, how
>long did it last?
(Now I'm REALLY dusting off the memory cells, remembering the
architecture of panel ...) While it could be argued that simply
adding a 21st. final frame to a panel office would expand the
capacity to 10,500 lines, I'm having a difficult time figuring
out how it could be shoehorned into the set-up of the incoming
frame, and addressed by the revertive pulsing, which was very
much hard-coded into the selection of one in 10,000 lines.
There were two revertive-pulse operations associated with the
incoming frame, which selected the final frame. The first was
a one-in-five selection which selected the brush to be used
or 'tripped', and the second was a one-in-four group selection
which selected one out of 20 final frames for a full office.
IIRC that second one-in-four was via a commutator which had
rather distant spacing. If you listened to the cadence of
the pulses coming back from a distant panel office, the very
first was rapid, and the second was quite a bit slower. A
vacant connection to the final frame in question was then
selected within that group.
In order to add a 21st. final frame, that group selection would
need to be a one-in-five, which implies that a fifth group
would need to be added to all banks of the incoming frame with
a modified commutator and quite a bit of wastage in the process.
I think maybe what happened is more along this line, which is
purely speculation on my part since I wasn't even aware of any
8 digit local numbers until long after I knew how a panel
office worked.
My guess is that new 'machine switched' offices were installed
with 10,000 lines and converted manual offices were truncated
or renumbered to 10,000 lines. However, I think that some of
the legacy 8 digit numbers may have been dialable via the
Panel Call Indicator on the B board of the legacy manual office.
I don't remember many of the details of PCI, but I do know that
it was quite versitile and used for things other than just an
indication to a B operator. I'm sure it would be possible for
a register-sender in an early panel office to be provisioned to
accept an eighth digit, with timeout in ambiguity cases, using
simple relay logic.
>I presume as preparations for DDD came along the
>eight digit subscribers got new numbers.
My guess is that when manual offices were converted to that
newfangled machine switching, the numbers above 9999 were
retired.
Your citation of 1947 listings of 8 digit numbers does imply
that they were dialable, since there was a LOT of panel in
service in those days and the post-war deployment of the #1
crossbar was replacing the remaining manual offices. I
doubt very seriously that a dial subscriber had to go out of
procedure and dial 0 Operator to be connected to those few
8 digit numbers. ;-)
My final conclusion is that HO5 (465 or legacy HOLlis) was
most likely still manual in 1947, soon to be converted to
crossbar, and that during the phase-in of dial, but prior to
DDD, yes, some 8 digit local numbers were indeed dialable.
Anyone care to refute (refudiate?) this ?? ;-)
Lisa or Jeff
> I'm trying to think back, and IIRC this (465) was panel in the
> early 70s, which would imply that it was converted from manual
> to dial (panel) prior to WWII. My impression of the age of the
> building was that it was definitely pre-war. �LOL, I could even
> drive you to where it was at the time. �;-) It could have been
> a #5 crossbar, making it possible that it was still manual in
> 1947. I do know that Chicago had some manual service into the
> mid 1950s, as did Omaha, home of Ma Bell's first full-scale
> panel deployment.
I understand that two large suburban exchanges in the Phila Metro area
didn't go dial until circa 1962 (FLanders in Upper Darby and Willow
Grove). What puzzles me is that FLanders was apparently dialable
using call indicators, but Willow Grove was not dialable and required
an operator to connect the call. A 1959 Phila White Pages did not
have any dialing instructions, to my surprise.
Converting a manual to dial office was extremely expensive and time
consuming. It took a number of years just to convert Manhattan, and
then longer for the outer boroughs. Further, some outer boroughs
weren't even developed until the postwar era.
The postwar era saw tremendous growth in the demand for phone
service. The Korean war and Cold War diverted telephone equipment. I
saw a postwar photo of a suburban Phila exchange (Ambler, PA) where
additional switchboard positions were clearly shoe-horned in a
building--one position was squeezed at an angle in a corner as part of
the multiple. The neighborhood served by the HOllis exchange had
postwar growth, perhaps they had to squeeze in eight digit numbers as
a temporary expedient.
I've heard the New York Public Library has old phone books going back
years. If they have one for Queens it may explain this.
The Bell Labs history notes that a new panel exchange was installed in
the NYC area around 1950. This is surprising. Presumably they wanted
compatibility with other equipment rather than using a No. 1
crossbar. Also they said new pieces of panel were added for many
years.
> I was far more familiar with the Floral Park office, not too
> far east of the Hollis office, which was at the time a #5
> crossbar, to which I've referred here in the Digest on occasion.
> This was unique in that it served both 212 and 516 prefixes at
> the time. �But back to the subject ...
In Phila, there were two city offices that served the nearby adjacent
suburbs (ESsex in Cheltenham was served out a lower NE Phila office,
and MElrose in Melrose Park was served out of the WAVerly office).
What was curious is that calls to and from those suburban exchanges
were billed at the suburban message unit rate even though they came
out of a city office. That is, someone in downtown Phila calling the
lower NE would be charged as a city call, but calling Cheltenham meant
message units. I think those arrangements continue to this day,
though they call it "Measured Service" and they've reduced the charges
from the past.
> My guess is that new 'machine switched' offices were installed
> with 10,000 lines and converted manual offices were truncated
> or renumbered to 10,000 lines. �However, I think that some of
> the legacy 8 digit numbers may have been dialable via the
> Panel Call Indicator on the B board of the legacy manual office.
I'm starting to wonder if the HOllis-5 office was manual. Did panel
switchgear store the entire phone number before acting on it, or did
it translate the exchange and then route the rest of the dial pulses
to the desired exchange? I understand your point of the frames, but
perhaps only the incoming storage register had to be larger.
> I don't remember many of the details of PCI, but I do know that
> it was quite versitile and used for things other than just an
> indication to a B operator. �I'm sure it would be possible for
> a register-sender in an early panel office to be provisioned to
> accept an eighth digit, with timeout in ambiguity cases, using
> simple relay logic.
The B operator's display is shown in many articles about panel (though
I don't know where there's one on the web). The display actually has
capacity for _nine_ digits: the leading 0/1 for eight digit numbers,
the four numbers, and a party line suffix letter. (I suppose these
could've been dialed, too.)
That the display has this capacity is what makes me believe eight
digits were dialable.
> >I presume as preparations for DDD came along the
> >eight digit subscribers got new numbers.
>
> My guess is that when manual offices were converted to that
> newfangled machine switching, the numbers above 9999 were
> retired.
Agreed. In the postwar era, while many subscribers had little change
to their numbers, others did. Sometimes it would get tricky--I've
seen special announcements printed for a community detailing the new
phone numbers.
jsw
>switchgear store the entire phone number before acting on it, or did
>it translate the exchange and then route the rest of the dial pulses
>to the desired exchange? I understand your point of the frames, but
>perhaps only the incoming storage register had to be larger.
It acted as soon as it had enough information to act. This was very
innovative for the technology of the day.
IIRC, the action on the dialed digits was somewhat overlapping on
panel. It was definitely not direct control by any means. If you
would dial slowly when calling one panel office from another, you
could often make out the sounds of the progress through the switch
train. The cadence of the sounds was quite different when calling
a #1 or #5 crossbar from a panel office than it was when calling
another panel office, and this made it somewhat easy to tell which
offices were panel and which were crossbar.
Of course if a tandem office was involved, things got interesting.
But anyway ... lots of this is from memory so some of the details
may be a bit off ...
Nothing really happened until the three digits of the office code
were dialed, then the register-sender called upon the translator
or decoder to get the orders on where to set the district (and
office frame, if used) frame to get to the terminating CO. You
could usually hear some scratches and clunks as this happened.
The rest of the process was well known by 'enthusiasts' as the
revertive pulsing was 'hard coded' to the particular directory
numbers. The register-sender in the originating office always
'knew' exactly where to set the incoming and final frames for a
particular 4-digit number. To hear this you would pause after
dialing the office code.
When you dialed the fourth digit, the first digit of the line
number in the distant CO, you would hear a 'scratch' of revertive
pulsing as the brush of the incoming frame was selected. Then
when you dialed the fifth digit, you would get more of a
'clack-clack-scratch' as the incoming frame advanced and the
final frame brush was selected. The last two digits gave you
that 'scratch-scratch-CLUNK' as the final frame advanced and
connected. IIRC this was two separate operations, the second
at a lower speed.
#include <one-ring-then-busy-on-a-busy-line-on-panel.h> ;-)
>The B operator's display is shown in many articles about panel (though
>I don't know where there's one on the web). The display actually has
>capacity for _nine_ digits: the leading 0/1 for eight digit numbers,
>the four numbers, and a party line suffix letter. (I suppose these
>could've been dialed, too.)
Party lines were all but gone in the city when I became interested
in such things, but I do remember references to manual exchanges
using lettered suffixes instead of assigning party line subs their
own directory number. This would mean that a full manual office
could very well handle well over 10,500 subscribers and that yes,
there could be numbers of the pattern FNOrd 2368j and and even
FNOrd 10015j and such. Now could those numbers be dialed by the
early dial subscribers? I have no clue! ;-) 'Maybe' is my best
guess. ;-)
PCI was very powerful, and could handle arbitrary digits and such
as long as the equipment was able to handle it. When dialing
from a panel office to crossbar, it was very easy to confuse the
sound of revertive pulsing (the cadence of which was far more
consistent in crossbar offices) with that of PCI.
Revertive pulsing could handle that 1 of 10000 selection, and in
cases of panel offices, could not do such things as deliver an
office code. (Yes, purists, I do know what 'high-5 is'.) ;-)
PCI was what was typically used when routing calls from a panel
office via a tandem office. The XBT crossbar tandem (think of a
#1 crossbar on steroids) typically received calls using PCI and
then sent them to the terminating CO via revertive pulsing.
There was also a panel tandem, and I'm sure it worked more or
less the same way, but these were all gone by the time I got
interested in these things.
ObTrivia: The only practical way of subscriber dialing between
panel and step offices was to go via a tandem which spoke all
of PCI, dial pulsing, and revertive pulsing.
>What puzzles me is that FLanders was apparently dialable
>using call indicators, but Willow Grove was not dialable ...
My guess here is that your Willow Grove office used some kind of
manual equipment (AE?) which did not support PCI or else was
planned for conversion and never intended to be dialable. I
would, however, think that it would be cost-effective in any
case of medium to long-term continuation of manual service to
convert to PCI, since the labor saving would be significant.
>The neighborhood served by the HOllis exchange had
>postwar growth, perhaps they had to squeeze in eight digit
It's been my impression that such offices as Floral Park and
Bayside (coincidental pun, located right by Bell Blvd.) ;-)
were postwar expansions intended to handle just this. I would
put money on the fact that some of the territory now served
by the Floral Park office (physically outside of the city but
serving a number of 212 numbers in my day) were originally
handled out of the Hollis office.
>The Bell Labs history notes that a new panel exchange was installed in
>the NYC area around 1950. This is surprising. Presumably they wanted
>compatibility with other equipment rather than using a No. 1
>crossbar.
My hunch here is that they wanted to use up existing inventory
of panel gear. Remember that the #1 crossbar was essentially a
drop-in work-alike of a panel office using newer technology.
>Also they said new pieces of panel were added for many
>years.
I do know that many panel offices were built out to the full
10,000 lines using panel technology instead of being upgraded
to crossbar.
I also vaguely remember a case in lower Manhattan (Broad St
CO, maybe?) where a to-be-upgraded panel switch was left in
service and the 1E intended replacement was put in service
to increase capacity.
***** Moderator's Note *****
PCI is "Panel Call Indicator", the system that lit the indicating
lights on the "B" operator's board.
Bill Horne
Moderator
Richard
<hanc...@bbs.cpcn.com> wrote:
>The Bell Labs history notes that a new panel exchange was installed in
>the NYC area around 1950. This is surprising. Presumably they wanted
>compatibility with other equipment rather than using a No. 1
>crossbar. Also they said new pieces of panel were added for many
>years.
When I joined Bell Labs in 1959, I had a series of classes about
introduction to the Bell System. In one of them, the instructor said
that Bell Labs invented the panel switch because they wanted the
flexibility of an X-Y switch like crossbar, but did not want to pay
royalties to the inventor of crossbar. He said that panel was clunky
and more prone to breakdown, but it beat paying royalties. I don't
know who was the invetor of crossbar.
Dick
jsw
>introduction to the Bell System. In one of them, the instructor said
>that Bell Labs invented the panel switch because they wanted the
>flexibility of an X-Y switch like crossbar, but did not want to pay
>royalties to the inventor of crossbar.
The story I heard and believed was that Ma Bell did not embrace
STEP technology because they did not want to pay royalties to
Strowger and company. Add to that the fact that direct-control
step does not scale well, of course. I never heard that story
about crossbar. Of course I never had the opportunity to attend
an orientation session at Bell Labs. ;-)
I guess they did eventually employ SxS for many smaller communities
in their service areas, and even some mid-size cities as well,
with Des Moines being an example.
>I don't know who was the invetor of crossbar.
I always assumed it was Bell Labs !! ;-) At least in the context
of telephone switching that is.
>He said that panel was clunky and more prone to breakdown
I don't think anybody is gonna argue with you over that. ;-)
You must admit, however, that for its time (the 19-teens) it
was very innovative and high-tech, even though it's been said
that the design was inspired by Rube Goldberg. ;-)
The story (legend) that was circulated among 'hobbyists' in
long-ago decades was that the panel switch was originally an
automated B board and was designed as an electromechanical
representation of a 'panel' of jacks with the selector rods and
brushes representing the operator's arm and plug. The revertive
pulsing was representative of the A operator telling the B
operator where to plug in the cable. ;-) 'Keep going, keep
going, no, higher .. keep going .. STOP!'
IIRC there were a few of these B board panel installations in
the 19-teens, long before the first full-scale panel roll-outs
in Omaha and Paterson.
Sam Spade
>
> I guess they did eventually employ SxS for many smaller communities
> in their service areas, and even some mid-size cities as well,
> with Des Moines being an example.
>
The Bell area of Los Angeles was all SxS in until after the war.
Richard
wrote:
>The story I heard and believed was that Ma Bell did not embrace
>STEP technology because they did not want to pay royalties to
>Strowger and company.
Beginning in 1965, I lived in Salem, NH and worked in the Lawrence, MA
area. Both Salem and Lawrence were NE Telephone and both had step
offices.
Both cwntral offices allowed last-5-digit dialing when calling phone
in the same respective city. Both 5- and 7-digit dialing worked.
In Salem, the office codes were 893 and 898. So a call to 898-8123
could be dialed as 88123. Then, the NH PUC ordered that our local
area include Nashua, NH, with office codes begining with 88
(882, 883, ... 888, 889). To make this work, NE Tel had to change the
Salem numbers of the form 898-8xxx to 893-0xxx, so that any dialing
beginning with 88 would be directed to Nashua. 5-digit dialing still
worked from Salem to Salem.
In Lawrence, the office codes began with 68 (681, 682, etc.) 5-digit
dialing existed for a long time. Some long time residents were so
used to the 5-digits that they would give their number as
"68 (pause) 23456" instead of "682 (pause) 3456".
Dick
Wes Leatherock
> I'm starting to wonder if the HOllis-5 office was manual. Did panel
> switchgear store the entire phone number before acting on it, or
> did it translate the exchange and then route the rest of the dial
> pulses to the desired exchange? I understand your point of the
> frames, but perhaps only the incoming storage register had to be
> larger.
>
> It acted as soon as it had enough information to act. This was very
> innovative for the technology of the day.
>
> IIRC, the action on the dialed digits was somewhat overlapping on
> panel. It was definitely not direct control by any means. If you
> would dial slowly when calling one panel office from another, you
> could often make out the sounds of the progress through the switch
> train. The cadence of the sounds was quite different when calling a
> #1 or #5 crossbar from a panel office than it was when calling
> another panel office, and this made it somewhat easy to tell which
> offices were panel and which were crossbar.
I thought panel offices used revertive pulsing, i.e. after the full
number was dialed the distance office started pulsing back to the
originating office until the originating office said "stop" and went
on to the next digit similarly. The first No. 1 crossbar offices were
arranged to simulate panel offices in their signalling, leading to the
apparent absurity of two No. 1 crossbar offices each simulating
panel's revertive pulsing. The first No. 1 crossbar was intended for
use in an all-panel environment.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Wes Leatherock
--- On Fri, 12/17/10, jsw <j...@ivgate.omahug.org> wrote:
{...]
> I guess they did eventually employ SxS for many smaller communities
> in their service areas, and even some mid-size cities as well, with
> Des Moines being an example.
How about Houston, Dallas, Los Angeles, Oklahoma City, Fort Worth,
Tulsa, Wichita, Little Rock.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Sam Spade
Lisa or Jeff
> The story I heard and believed was that Ma Bell did not embrace
> STEP technology because they did not want to pay royalties to
> Strowger and company. Add to that the fact that direct-control
> step does not scale well, of course. I never heard that story
> about crossbar. Of course I never had the opportunity to attend
> an orientation session at Bell Labs. ;-)
The Bell Labs history says that by 1900 manual switchboards were
highly developed and from the subscriber's point of view, easy to
use. In contrast, the Strowger switch at that time wasn't as
developed, such as requiring subscribers to ring manually. It was
also expensive since it was a large capital outlay. Manual offices
didn't need operators--saving wages--during off peak hours. Only very
tiny offices were seen as candidates for dial since there wasn't
enough traffic to justify even a single operator. (However, for many
years Bell had such light duty operators in private homes, see the
Mountain Bell history for a description.)
The Bell Labs history says Bell made many improvements in the Strowger
switch for Bell Service.
Note that by the time dial was perfected it took about 50 years to
convert all Bell System lines to dial (Santa Catalina Island. being
the last). That's a long time. Conversion to dial was a major
undertaking. Some manual exchanges were converted directly to ESS.
> I guess they did eventually employ SxS for many smaller communities
> in their service areas, and even some mid-size cities as well,
> with Des Moines being an example.
Step by step handled the majority of dial lines of the Bell System.
Plenty of mid sized cities had it. SxS lines peaked in 1974.
> You must admit, however, that for its time (the 19-teens) it
> was very innovative and high-tech, even though it's been said
> that the design was inspired by Rube Goldberg. ;-)
I wonder if its developers used tools like Boolean algebra to work out
the logic.
> IIRC there were a few of these B board panel installations in
> the 19-teens, long before the first full-scale panel roll-outs
> in Omaha and Paterson.
I believe also in Newark, NJ. This made sense, as it gave Bell
engineers experience before the big rollout in NYC.
* * * *
>In Lawrence, the office codes began with 68 (681, 682, etc.) 5-digit
>dialing existed for a long time. Some long time residents were so
>used to the 5-digits that they would give their number as
>"68 (pause) 23456" instead of "682 (pause) 3456".
Five digit dialing lasted for a long time in small towns. Yes,
residents did refer to their numbers in the above fashion. Also,
stationery listed a business phone as (311) 55 5-2368, with a space in
the exchange.
A resident of a such a small town told me the phone company told
people to use 7 digits and stopped referring to 5 digits. But 5
digits continued to work until the exchange was cutover to ESS. (He
hoped to get a switch unit after the cutover but the old gear was kept
quite secure. I would think its value would only be scrap by that
point in time.)
Robert Bonomi
jsw <j...@ivgate.omahug.org> wrote:
>I guess they did eventually employ SxS for many smaller communities
>in their service areas, and even some mid-size cities as well,
>with Des Moines being an example.
>
I was never in an actual C.O. in Des Moines, but in the mid 60's, I did
belong to an Explorer Scout troop that met at the Bell training facility
downtown.
There was a _small_ practice switch where we met -- the switching elements
did -not- resemble any of the pictures I find on-line of a Strowger SxS relay,
was definitely -not- crossbar, and I'm not having any luck finding a decent
picture of either a 'rotary' or 'panel' switching element, to validate my
recollections against. Recollection is a gizmo that processed a two-digit
chunk of a number -- a disk element that rose on a rod for the first digit,
and rotated for the second one. *guessing* (=very= roughly, at a 45-year
remove) at a circa 1-1/2" dia, and a vertical travel of 6-8".
Neal McLain
> wesr...@aol.com
Or Carbondale IL, Ann Arbor MI, or Centerville IA?
http://tinyurl.com/yv6wyy
Neal McLain
jsw
Wes Leatherock wrote:
> I thought panel offices used revertive pulsing, i.e. after the full
> number was dialed the distance office started pulsing back to the
> originating office until the originating office said "stop" and went
> on to the next digit similarly.
It's always been my understanding, and I'm fairly certain of this,
that on the panel offices which were common in the late 60s and
early 70s, the dialing and outpulsing could be overlapping, in
that once the office code was dialed, the register-sender of the
originating panel office seized a trunk to the terminating office
and as digits were dialed, the call progressed accordingly.
The revertive pulsing corresponded to the four digits in that
each four-digit line number had a definite sequence of revertive
pulsing, but it was not four actions, not one per digit, it was
five.
A true panel office was very noisy in that the sounds of the
office could be heard during and immediately after dialing. I
really think that a lot of people who are otherwise very CO
savvy are forgetting this. Panel offices were also notoriously
noisy during the connection. Contacts were often microphonic.
One sound was kind of a cross between a 'clang' and the sounds
of chains rattling.
You could clearly hear the progress of the call when you were
dialing from a true panel office. Not as much from a #1 or #5
crossbar. Most users simply dialed away, but those who were
interested in such things would often pause and listen closely
when dialing.
Many phone 'enthusiasts' were quite familiar with the sounds of
the quirky panel offices, and knew the following operations quite
well:
1. When the thousands digit was dialed, there would be one burst
of revertive pulsing which could usually be heard. It was heard
as a brief 'scratch', and was that one-in-five selection of the
brush on the incoming frame.
2. When the hundreds digit was dialed, there would be TWO bursts
of revertive pulsing, the first being that one-in-four group
selection as the incoming frame selector advanced, and the second
as a one-in-five selection of the brush on the final frame. This
would sound like a 'clack-clack-clack-scratch' when calling from
a panel office to a panel office, and more like a 'scratch-scratch'
when calling from a panel to a crossbar office.
3. The last two digits, of course, selected the one-in-100 position
of the final frame selector. IIRC, the second 'scratch' in this
sequence was a bit slower when calling a panel office than when
calling a crossbar office.
>The first No. 1 crossbar offices were arranged to simulate
>panel offices in their signalling, leading to the apparent
>absurity of two No. 1 crossbar offices each simulating panel's
>revertive pulsing. The first No. 1 crossbar was intended for
>use in an all-panel environment
IIRC, the register-sender (or what it's properly called on a #1
crossbar) did record all digits before seizing the trunk to the
distant CO, but I'm not 100% sure of this. There may very well
have been some overlap, as I remember that when the 1E offices
started coming out around 1970, a call from a #1 crossbar office
to a crossbar/panel office went through very quickly, where a
similar call from a 1E office had a delay of about a second after
all digits were dialed.
> How about Houston, Dallas, Los Angeles, Oklahoma City, Fort Worth,
> Tulsa, Wichita, Little Rock.
I don't know about any of these except Los Angeles, and it's
been my understanding that quite a bit of the El-Lay area was
indie using AE step, and Ma Bell simply went along. ;-) I do
know that there was quite a bit of #5 crossbar in Orange
County in the early 1970s, as well as some 1E making inroads
into the area as well. I vaguely recall much of Santa Ana
being step as well.
Our own Pat has eluded to the Wabash office in Chicago being
step, but I kind of question this, since I know a lot of
Chicago was panel and #1 crossbar from the 30s through the
70s.
Sam Spade
>
> Our own Pat has eluded to the Wabash office in Chicago being
> step, but I kind of question this, since I know a lot of
> Chicago was panel and #1 crossbar from the 30s through the
> 70s.
>
Alas, there used to be a web site with recordings of all those switch
sounds, including panel.
Wes Leatherock
--- On Sat, 12/18/10, Lisa or Jeff <hanc...@bbs.cpcn.com> wrote:
> A resident of a such a small town told me the phone company told
> people to use 7 digits and stopped referring to 5 digits. But 5
> digits continued to work until the exchange was cutover to ESS.
Many were converted to 5XB much sooner than ESS became viable. That
also prevented five-digit dialing.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Lisa or Jeff
> A true panel office was very noisy in that the sounds of the
> office could be heard during and immediately after dialing. I
> really think that a lot of people who are otherwise very CO
> savvy are forgetting this. Panel offices were also notoriously
> noisy during the connection. Contacts were often microphonic.
> One sound was kind of a cross between a 'clang' and the sounds
> of chains rattling.
At ACTA and TCI phone shows, sometimes collectors bring in working
switches to demonstrate, including panel. Visitors can make calls on
them. Sometimes different exhibitors link their switches together.
(Sometimes they use electronic black boxes to accomoplish the
interface).
When I watched the panel frame work, the motor and rods were quiet,
certainly quieter than the ratchet of the step-by-step switch or the
relaxy clacking in a cross bar. Of course that was but a single
frame, maybe a room full of them and associated might be different.
Check ACTA and TCI websites for shows--they are held all over the
country and Canada. Worth a visit if not too far away.
> I don't know about any of these except Los Angeles, and it's
> been my understanding that quite a bit of the El-Lay area was
> indie using AE step, and Ma Bell simply went along. ;-) I do
> know that there was quite a bit of #5 crossbar in Orange
> County in the early 1970s, as well as some 1E making inroads
> into the area as well. I vaguely recall much of Santa Ana
> being step as well.
I think LA was step because it had many independents that Bell took
over and in that particular case it was easier to leave it as is. But
I suspect given the size and growth of LA it would've been panel or #1
crossbar to facilitate inter-office networking and trunk utilization.
They attempted some SxS front end common control in LA to improve
efficiency. SxS also had something called the "graded multiple" which
improved trunk utilization.
> Our own Pat has eluded to the Wabash office in Chicago being
> step, but I kind of question this, since I know a lot of
> Chicago was panel and #1 crossbar from the 30s through the
> 70s.
Downtown Phila had some SxS units serving certain Centrex users.
Oddly, SxS but not panel could service Centrex. On a small
organization that had centrex via SxS, on interoffice calls the first
digit was absorbed and users need only dial the last three digits
(this was not well known). The organization's switchboard was a
traditional cord unit, too; most Centrex's had consoles for the
operators.
Harold Hallikainen
> people to use 7 digits and stopped referring to 5 digits. �But 5
> digits continued to work until the exchange was cutover to ESS. �(He
> hoped to get a switch unit after the cutover but the old gear was kept
> quite secure. �I would think its value would only be scrap by that
> point in time.)
In the early 1970s, Santa Maria CA had a step switch (General
Telephone at the time). They had 5 digit dialing. I worked in radio
stations in both Santa Maria and San Luis Obispo (Pacific Telephone).
SLO had 7 digit dialing. Santa Maria is right on the county line. The
radio stations in Santa Maria I worked for would give business
telephone numbers as 5 digits. Listeners across the county line could
not dial the numbers that way. Santa Maria's switch would accept 7
digit numbers. I always thought they should broadcast 7 digit numbers
to be useful to the largest number of listeners. Of course, when 7
digit numbers were broadcast, the prefix was WAlnut 5.
Also at that time, you had to go through an operator to call from SLO
to Guadalupe, a town west of Santa Maria. I don't know if Santa Maria
could dial Guadalupe direct or if, perhaps, Guadalupe still had a
manual switch at that time.
Harold
Wes Leatherock
--- On Sun, 12/19/10, jsw <j...@ivgate.omahug.org> wrote:
{ ... ]
> I don't know about any of these except Los Angeles, and it's been my
> understanding that quite a bit of the El-Lay area was indie using AE
> step, and Ma Bell simply went along. ;-) I do know that there was
> quite a bit of #5 crossbar in Orange County in the early 1970s, as
> well as some 1E making inroads into the area as well. I vaguely
> recall much of Santa Ana being step as well.
The first dial office in Oklahoma City, installed by the Bell company
in 1920, was AE step equipment ordered through WE as required, since
WE did not make step equipment at that time.
In 1927, the rest of the city was coverted to dial with WE SxS
equipment.
The AE equipment remained compatible with additions to the first (AE)
office being made with WE equipment. In the late 1950s I remember we
put out a news story that the ringing sound would be different in that
office because the old (AE) ringing machine was being replaced. It
was being replaced, not from failure, but because with the continued
growth of the office it had reached its capacity. Ten or 20 years
later the entire office was replaced with ESS.
It was like a picture out of history books to see the AE line switches
in their glass cases. Of course all the later additions used line
finders.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Lisa or Jeff
I recently heard that on You-Tube there are recordings of such sounds.
* * * *
Regarding the number of proportion of various switch types, the Bell
Labs history books have some statistics, but they're buried in
footnotes and not indexed, so they're hard to find. (If I find them
up I'll post them.)
What is interesting is that for each switch type there are two
statistics that are not at the same time. One statistic is the
maximum proportion the switch held, and the other, usually later, is
the maximum number of lines served by that switch.
For example, in its heydey, step-by-step was the biggest switch used
by the Bell System. But although other switches like crossbar and ESS
entered service, SxS continued to grow, with its peak volume occuring
in 1974.
Unfortunately, the history books were published before the completion
of ESS. I would be interested to see the stats on analog ESS and
digital ESS relative to the older types.
The statistics refer only to the Bell System. I don't know if the
independents, which tended to serve smaller locations, had panel;
though they did have their own crossbar and ESS. In one sense, very
small telephone companies may have had trouble getting capital to
replace their old SxS exchanges with ESS. But the footprintspace,
maintenance, and labor savings for ESS was a big issue, especially for
smaller community exchanges. Small exchanges were often unattended
and a serviceman sent out (driving a considerable distance) only when
necessary. ESS eliminated many of those trips. Small communities had
big growth but no physical room to expand the exchange, and again ESS
allowed that to happen. Finally, ESS allowed for new service options
and increased revenue.
* * *
Someone mentioned patents. According to the Bell Labs history, Bell
made a patent agreement with Automatic Electric to use their switches
(and presumably AE got use of Bell's improvements). In the early
years Bell contracted with AE to build switches for Bell under Bell
specs.
* * *
Regarding the choice of whether to automate a city with step or panel,
part of the decision depended on the expectation of future growth and
the need to interconnect _automatically_ with other exchanges. A city
not expected to grow that fast got step. Certain cities were
experiencing extremely rapid growth in the 1920s and they got panel.
Note that a big advantage of panel over step was in more efficient
trunk usage between offices thanks to panel's ability to translate
decimal numbers to whatever was needed for the trunk groups. Step got
cumbersome, especially with high traffic to other offices.
As to the interconnection, in cities a call from a dial exchange to a
manual one was often not a toll call and thus could be handled
automatically. The panel interface with manual boards worked out well
for that. But in towns where calls to a manual exchange was usually
toll, then an operator was required so the interface capability of
panel wasn't needed.
Panel had the capability to have a counter-meter for each subscriber
to count up local calls. Calls could be timed and the meter
incremented after each period, as they apparently were in NYC. I
don't believe Step got this capability until much later.
[The Bell Labs history spends quite a few pages on this subject.]
Joseph Singer
> Alas, there used to be a web site with recordings of all those
> switch sounds, including panel.
Well, it still exists:
http://www.wideweb.com/phonetrips/
jsw
>of a number -- a disk element that rose on a rod for the
>first digit, and rotated for the second one.
What you are describing, to a tee, is the final selector
or 'connector' in a Strowger (step) office.
The next to last digit, the 'tens' digit, would cause the
switch to ratchet upward, the number of levels being equal
to the digit on the dial, and the last digit, the 'units'
digit, would cause it to rotate into the bank to the line
being called.
#include <vertical_pawl stationary_dog double_dog etc.h> ;-)
The first and second (incoming) selectors would step upward
along with the dial pulses and then rotate to a vacant
connection to the selector for the next digit.
A distinct audible 'clunk' could always be heard right after
dialing the thousands and hundreds digits, as the selector
rotated and seized the next level selector, but not after
the tens digit. Similar clunks could be heard after each
digit when dialing the office code, but the clunk after the
first digit was often times masked by the extinction of the
dial tone.
>Downtown Phila had some SxS units serving certain Centrex
>users.
Columbia University used to have something like this in the
early 1970s. However, I always thought of it as more of a
step-based PBX with direct inward dialing than a true
'Centrex' with all of the switch-based bells and whistles
such as call transfer, three-way, camp-on and such.
The only 'feature' I remember on that particular installation
was that a hook flash would signal the human operator who
could then do a call transfer or (do I really remember this?)
three-way. IIRC, the operator was on a cord board. I also
seem to recall that this was all driven by a crossbar tandem.
>Oddly, SxS but not panel could service Centrex.
I can visualize that it would be very difficult to do any
kind of 'Centrex' type features on a panel office with the
totally inflexible architecture of the incoming and final
frames. I think that hunt groups were the most fancy of the
features that panel could do.
As I think back I can't think of any 'Centrex' or even any
DID-PBX installations hosted on a #1 crossbar. I do recall
some native #5 crossbar Centrex (or was it really DID-PBX, I
guess it's a matter of semantics) installations and I do
remember that #5 crossbar often times hosted the 101 ESS
Centrex-CU installations, but I don't recall any #1 crossbar
switches driving the 101 either.
Lisa or Jeff
> >Downtown Phila had some SxS units serving certain Centrex
> >users.
>
> Columbia University used to have something like this in the
> early 1970s. However, I always thought of it as more of a
> step-based PBX with direct inward dialing than a true
> 'Centrex' with all of the switch-based bells and whistles
> such as call transfer, three-way, camp-on and such.
>
> The only 'feature' I remember on that particular installation
> was that a hook flash would signal the human operator who
> could then do a call transfer or (do I really remember this?)
> three-way. IIRC, the operator was on a cord board. I also
> seem to recall that this was all driven by a crossbar tandem.
I believe the first version of Centrex was essentially a PBX with
direct inward dialing. Centrex II, which I think required ESS, had
more of the "bells and whistles" with automatic call transfer and
three-way, etc.
The older Centrex did transfers by hookswitch flash. For directly
dialed calls and calls handled by a cordless board, it showed up on
the operator's console. For calls handled by a cord board, it flashed
the cord circuit supervisory (hookswitch) lights.
> As I think back I can't think of any 'Centrex' or even any
> DID-PBX installations hosted on a #1 crossbar. I do recall
> some native #5 crossbar Centrex (or was it really DID-PBX, I
> guess it's a matter of semantics) installations and I do
> remember that #5 crossbar often times hosted the 101 ESS
> Centrex-CU installations, but I don't recall any #1 crossbar
> switches driving the 101 either.
I don't think #1 crossbar did much of anything beyond switch calls.
Indeed, the Bell Labs history, while discussing it, seems to downplay
its role, focusing all the accolades on the #4 (toll) and #5
crossbar. My impression is that the #1 xbar was merely a more cost-
efficient and trunk-efficient machine over panel, but didn't add
anything in the way of customer features. Of course being trunk
efficient was a major cost saving and one of the weaknesses of step in
high traffic situations.
The history says they tried call waiting on the #5 but it wasn't cost-
efficient to implement as a service on that machine.
Sam Spade
>
> The history says they tried call waiting on the #5 but it wasn't cost-
> efficient to implement as a service on that machine.
>
I am aware the SBC actually deployed some calling features on a No. 5
XBAR on the north side of Kansas City, MO. A friend of mine subscribed
to them circa late 1960s. I don't recall whether he was part of a test
group or whether it was a public offering for that particular switch.
Sam Spade
Wes Leatherock
--- On Mon, 12/27/10, jsw <j...@ivgate.omahug.org> wrote:
> What you are describing, to a tee, is the final selector
> or 'connector' in a Strowger (step) office.
If there is a rotary group customer on the final selector it will
search for a vacant line to that customer in the group just like in a
earlier seclector in the switch train. The last line is busied out in
the hunt group. If there is more than one hunt group, it works the
same when when dialing the first number in each group.
> The next to last digit, the 'tens' digit, would cause the
> switch to ratchet upward, the number of levels being equal
> to the digit on the dial, and the last digit, the 'units'
> digit, would cause it to rotate into the bank to the line
> being called.
>
> #include <vertical_pawl stationary_dog double_dog
> etc.h> ;-)
>
> The first and second (incoming) selectors would step
> upward
> along with the dial pulses and then rotate to a vacant
> connection to the selector for the next digit.
>
> A distinct audible 'clunk' could always be heard right
> after
> dialing the thousands and hundreds digits, as the selector
> rotated and seized the next level selector, but not after
> the tens digit. Similar clunks could be heard after
> each
> digit when dialing the office code, but the clunk after
> the
> first digit was often times masked by the extinction of
> the
> dial tone.
>
> As I think back I can't think of any 'Centrex' or even any
> DID-PBX installations hosted on a #1 crossbar. I do
> recall
> some native #5 crossbar Centrex (or was it really DID-PBX,
> I
> guess it's a matter of semantics) installations and I do
> remember that #5 crossbar often times hosted the 101 ESS
> Centrex-CU installations, but I don't recall any #1
> crossbar
> switches driving the 101 either.
When Phillips 66 headquarters in Bartlesville, Okla., adopted centrex,
the engineers determine it was chaper to make it a centrex-CO and
serve it out of the existing #5XB at the CO a block away.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Sam Spade
>
> A resident of a such a small town told me the phone company told
> people to use 7 digits and stopped referring to 5 digits. But 5
> digits continued to work until the exchange was cutover to ESS. (He
> hoped to get a switch unit after the cutover but the old gear was kept
> quite secure. I would think its value would only be scrap by that
> point in time.)
>
It could have continued to work with SPC. A standard feature in the
DMS-100 was 5 digit community dialing; i.e. dial the 5 digets plus the
"#" sign. So far as I know, no LECs opted to implement this feature.
It only saved one digit. But, with the advent of mandatory 10 digit
dialing it would be more desirable today.
Sam Spade
>I always thought they should broadcast 7 digit numbers
> to be useful to the largest number of listeners. Of course, when 7
> digit numbers were broadcast, the prefix was WAlnut 5.
>
I'm amazed at the number of trucks I still see on the road with their
7-digit telephone number.
jsw
>XBAR on the north side of Kansas City, MO. A friend of mine subscribed
>to them circa late 1960s.
This then confirms some rumors and speculation among 'enthusiasts'
that Ma Bell had developed some kind of a 'stored program engine'
for the #5 Crossbar that would replace the relay-logic markers and
senders and such, and give the #5 Crossbar the ability to do the
fancy Custom Calling Features<tm> just like the 1E.
This is the only first-person account I've heard of anything like
this actually happening. I assume that it was never really
rolled out simply due to the ESS deployment plans.
danny burstein
>Harold Hallikainen wrote:
Even more amazing is the prevalence of 7 digit numbers
in "welcome to mumble mumble" guidebooks...
--
_____________________________________________________
Knowledge may be power, but communications is the key
dan...@panix.com
[to foil spammers, my address has been double rot-13 encoded]
Wes Leatherock
--- On Wed, 12/29/10, Sam Spade <s...@coldmail.com> wrote:
>
> I'm amazed at the number of trucks I still see on the road
> with their
> 7-digit telephone number.
Why? In many placess with only one area code 10-digit dialing of a local number generates and error message to the caller.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Lisa or Jeff
I would presume that ESS could easily handle 5 digit dialing. But I
suspect it went away because there were too many other exchanges being
created and the 5 digits weren't enough to make the local exchanges
unique.
For instance, in border areas, residents could call across a state
line to the opposite town using only seven digits. That made the
exchange-codes in the border town had to be unique in _both_ area
codes. That was fine in the old days, but as they began to run out of
exchanges that was no longer workable. So, the border people had to
dial 10 or 11(+1) digits.
As an aside, the Bell history mentions that long ago (1960s) Bell
recognized they were running out of exchange-codes, and built/
programmed switches so that area codes could be an exchange code and
vice versa. I believe this meant that the 1+ prefix would be
necessary in places where it wasn't used before so as to differentiate
the call.
Regarding the previous posts regarding the term Centrex vs. "inward
dialing", it appears from the history that the function was developed
first and given a name later. In the early 1960s there were a few
different combinations of machine types that would support Centrex.
Some users had a 701 dial step-by-step PBX which was modified to
accept digits from the central office; others were served by a step-by-
step central office that was modified; still others were served by No.
5 crossbar or crossbar tandem. The two biggest features were direct
inward dialing and identification of outward dialed calls so as to
track charging and usage by extension. (I was employed at an
organization that had ONI for that.)
As time went on new features were added, such as automatic transfers
and loop access consoles instead of direct trunk. ESS added more
features.
Note that back then the switchgear was located about half at the
central office and half at the user's site. The tradeoff for central
office location--which meant all loops had to come from the CO--was
that repairmen didn't have to go out to the user's site for service.
Lisa or Jeff
I checked the Bell Labs History 1925-75 and it does not appear that
they hda replaced the relays with electronics in the common control
unit. They considered it:
"In 1970 a committtee studied the possibilities of modernizing the No.
5 crossbar by adapting stored-program control techniques. At that
time, electronic technology was not low enough in cost for the new
services to be provided at tariffs comparable with the ESS family and
for administration cost reductions."
It should be noted that about the same time Western Electric developed
a new electro-mechanical (crossbar) PBX, the 770A, that was more cost-
competitive than certain low-end ESS designs by Bell Labs. "Even
though electronics was clearly the way to the future, the 770A enjoyed
a number of years when it was the economic choice on a first-cost
basis over comparable designs."
(In 1970 I don't recall any electronic stand-alone cash registers, and
I don't believe they became commonplace--more cost effective--until at
least 10-15 years later. The cheap electronics we take for granted
today was still in the laboratory in 1970. Anyone know when NCR
ceased making stand-alone electro-mechanical and all-mechanical cash
registers?)
They used electronics and mini-computers to aid in translation, AMA
recording, and in signaling and timing circuits.
One innovation for No. 5 was the use of "wire spring" relays,
replacing the U and Y type flat spring relays in 1953-54.
They did experiment with custom calling features on No. 5 crossbar in
Columbus Ohio 1963-65, Iowa and Mass 1966, and Ohio 1971. They found
that those services were too expensive to be done in crossbar, so
rollout had to wait until ESS. They used piggyback twister memory in
some cases.
The book is a bit vague on whether these tests were by an electronic
or relay common control. I think the basic "logic" was still relay
circuits, especially because it was done in the early 1960s when ESS
itself was still under development. Further, the other comments above
suggest electronics were still too new. I suspect that if they had a
true electronic front end the cost of crossbar implementation would
not have been excessively expensive.
Last, all-new installations of No. 5 crossbar ended in 1976.
[I am condensing a considerable number of pages from the book for this
post. The footnotes refer to numerous Bell Labs Record articles for
the feature trials; I'll post the specifics if anyone is interested in
further research.]
But let's note that when it comes to machine "logic", a relay performs
the same function as a transistor or vacuum tube, it's only bigger and
slower. In the 1940s, IBM built sophisticated _programmable_
digital computers--the Harvard Mark I and its own SSEC using mostly
relay logic, and Bell Labs had a relay computer, too. Also in the
1940s, railroad switch control machines were deployed that used push-
button control to automatically route trains and avoid all conflicting
movements; these utilized extensive relay logic to test choices for
safety and then execute the commands to switches and signals on the
tracks. Thus, by the 1960s it certainly was possible for relay logic
to handle features like call waiting.
Neal McLain
> --- On Wed, 12/29/10, Sam Spade <s...@coldmail.com> wrote:
>
>
>
> > I'm amazed at the number of trucks I still see on the road
> > with their
> > 7-digit telephone number.
>
> Why? In many placess with only one area code 10-digit dialing
> of a local number generates and error message to the caller.
Possibly because trucks sometimes venture outside of their home area
codes?
Neal McLain
Sam Spade
>
>
> --- On Wed, 12/29/10, Sam Spade <s...@coldmail.com> wrote:
>
>
>>I'm amazed at the number of trucks I still see on the road
>>with their
>>7-digit telephone number.
>
>
> Why? In many placess with only one area code 10-digit dialing
> of a local number generates and error message to the caller.
Why? Because where I see them is in the greater Los Angeles area, or
Seattle, etc.
Sam Spade
Where I live, that takes 20 minutes at 75 on the freeway. :-)
Then, there are overlays.
Wes Leatherock
--- On Wed, 12/29/10, Lisa or Jeff <hanc...@bbs.cpcn.com> wrote:
[ ... ]
> Regarding the previous posts regarding the term Centrex vs. "inward
> dialing", it appears from the history that the function was
> developed first and given a name later. In the early 1960s there
> were a few different combinations of machine types that would
> support Centrex. Some users had a 701 dial step-by-step PBX which
> was modified to accept digits from the central office; others were
> served by a step-by- step central office that was modified; still
> others were served by No. 5 crossbar or crossbar tandem. The two
> biggest features were direct inward dialing and identification of
> outward dialed calls so as to track charging and usage by extension.
> (I was employed at an organization that had ONI for that.)
The first applicatins of DID in Southwestern Bell territory were at
military bases--first Fort Sam Houston, Texas, and then at Fort Sill,
Oklahoma.
Both of these were technically government-owned and operated PBXs. I
don't know about Fort Sam, but Fort Sill was a step-by-step switch, I
believe AE although I'm not sure. A prefix was assigned and off-base
phones could then dial directly to what was formerly the extension
number. (Before that you dialed the main number and a
soldier/operator answered and dialed the extension you wanted.)
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Andrew Carey
>> I am aware the SBC actually deployed some calling features on a
>> No. 5 XBAR on the north side of Kansas City, MO. A friend of mine
>> subscribed to them circa late 1960s.
>
> This then confirms some rumors and speculation among 'enthusiasts'
> that Ma Bell had developed some kind of a 'stored program engine'
> for the #5 Crossbar that would replace the relay-logic markers and
> senders and such, and give the #5 Crossbar the ability to do the
> fancy Custom Calling Features<tm> just like the 1E.
>
> This is the only first-person account I've heard of anything like
> this actually happening. I assume that it was never really rolled
> out simply due to the ESS deployment plans.
Not Ma Bell, but there was such a system in the late '80s or early
'90s called CONTAC BASE from Network Access Corporation that served as
a front end and provided SS7 and CLASS features. I never had any
direct dealings with it so I'm hazy on the details. One of their
patents (4,853,955) is SS7 for the crossbar & 1/1A ESS. 4,903,263 is
another one for ISDN through the same.
jsw
>search for a vacant line to that customer in the group just like in a
>earlier seclector in the switch train. The last line is busied out in
>the hunt group.
This answers for sure one thing I've kinda been curious about, but
it reminded me of one thing I have never understood.
I always assumed that there would be something like that leaf switch
to catch that all lines busy condition and return line busy to the
caller, kind of like that 11th. step contact set on the other
selectors. This explanation does make perfect sense.
One thing I'm still puzzled about ...
Is it possible on a Step office to have a hunt group with more
than 10 (9) lines?
Was there maybe some circuitry to sense when all lines on a
given level were busy and cause it to step upward one more
level?
I can see how this might be done with a set of vertical
contacts, similar to that on the linefinder, but I never
recall hearing about anything like this in service.
Do you (anybody?) know?
Sam Spade
>
> Is it possible on a Step office to have a hunt group with more
> than 10 (9) lines?
I can't answer how it was done but I know it was done. The branch L.A.
County Superior Court in Pomona was in GTE-land and served by a stepper
in the 1970s. I would call the court at a busy time and hear it
ratcheted through 10 clicks, a brief pause and then another 10 clicks
before it returned a line busy signal. So, it would seem they had 20
lines in hunt.
No circle hunt, though. :-)
Wes Leatherock
--- On Tue, 12/28/10, jsw <j...@ivgate.omahug.org> wrote:
>
> One thing I'm still puzzled about ...
>
> Is it possible on a Step office to have a hunt group with more than
> 10 (9) lines?
>
> Was there maybe some circuitry to sense when all lines on a given
> level were busy and cause it to step upward one more level?
>
> I can see how this might be done with a set of vertical contacts,
> similar to that on the linefinder, but I never recall hearing about
> anything like this in service.
>
> Do you (anybody?) know?
That's exactly how it was done.
Most groups weren't that big, but in Oklahoma City there was an
incoming group of almost 100 "800" numbers which was routed through a
step office (because of capacity reasons) because the 4A could not
connect to and signal a subscriber line because it did not provide for
the usual supervision. (off-hook, on-hook?) One of the local engineers
figured out how to add one relay on the 4A that would allow it to
supervise as a subscriber line. (he had first asked Bell Labs and
then said it couldn't be done; aftet he reported to the Labs how he
had done so a letter came out from the Labs describing the method.)
That saved a lot of holding time throught the network because every
incoming call previously had to wait while the call progressed with
step pulses.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Lisa or Jeff
> Is it possible on a Step office to have a hunt group with more
> than 10 (9) lines?
>From the Bell Labs history:
"Due to the limited access inherent in each level of the sxs switch,
much effort was expended to obtain efficient gradings. In addition
the concept of providing access greater than 10 was adopted. This was
done by introducing an additional stage of 22 terminal switches, known
as rotary out-trunk selectors to reduce the number of succeeding
switches and trunks."--Ref. Trunk hunting Switches, Record, Dec 1928;
Improved Graded Multiple for sxs offices, Record Sept 1944.
"At the terminating end of the switch train, new level-hunting
connectors were developed that enabled the system to serve PBXs with
more than ten trunks without the grading of the connector multiple,
thereby obtaining better call completion." --Ref. "Level Hunting
Connectors" Bell Labs Record March 1929.
See also Bell Labs Record Sept 1927.
[It would be great if they could put old issues of the Record on-
line.]
Wes Leatherock
> "At the terminating end of the switch train, new level-hunting
> connectors were developed that enabled the system to serve PBXs with
> more than ten trunks without the grading of the connector multiple,
> thereby obtaining better call completion."
>
> --Ref.> "Level Hunting Connectors" Bell Labs Record March 1929.
I went to the University of Okloahoma for two years and Oklahoma A&M
College (now Oklahoma State University for two years when Norman and
Stillwater were both manual offices. The OU number was 900 and the
Oklahoma A&M number was 1380.
When you asked the operator for the number you could hear them running
the tip over the group busy jacks (which emitted a tone) and when they
came to one that wasn't busy you could hear them running the jack
laterally then to find an unbusy line. The operators were so adept
that it took a while to realize what they were doing because it was so
fast the delay was not much more than the usual busy test on a single
line.
The group busy jacks I believe governed a strip of 20 jacks just to
the side in the multiple. They corresponded to the level hundting on
the SxS switches.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Wes Leatherock
Rotary equipment from IT&T and other sources which signaled just like Panel
Type offices would circle hunt.
Wes Leatherock
wlea...@yahoo.com
wes...@aol.com
Lisa or Jeff
> I always assumed that there would be something like that leaf switch
> to catch that all lines busy condition and return line busy to the
> caller, kind of like that 11th. step contact set on the other
> selectors. �This explanation does make perfect sense.
I'm not sure how it was done, but every step switch had a number of
relays mounted on it for various logical functions, such as
controlling the hunt for an empty line or returning a busy signal.
One waste of step by step was that this "logic unit", though small,
was tied up on every switch for the duration of the call. If a call
required seven digits, that was seven logic units tied up.
> Is it possible on a Step office to have a hunt group with more
> than 10 (9) lines?
Please see the separate posts on this subject.
That undoubtedly had to be solved early because even in the early days
there were many organizations that had more than ten incoming trunks.
One other observation about step vs. panel in the early days: As
mentioned, step originally was not very sophisticated and required
certain manual operations on the part of the subscriber, such as
pushing a ringing key. Bell added some innovations to make the call
progress as automatic as possible from the point of view of the
subscriber--lifting the receiver initiated various actions and hanging
up initiated various restore actions. It also converted step from
local-battery to common-battery. (see the 1875-1925 history for more
details on this).
Bell felt manual exchanges were more appropriate for medium and small
sized cities cira 1910-1920. Operators were only on duty and paid
when needed, as opposed to expensive automatic switchgear which sat
idle when not needed. Manual switchboards were relatively cheap
compared to automatic switchgear.
Bell also felt the 10x10 step by step matrix would be inadequate for
city service due to the numerous exchanges, which is why they
developed panel.
For the most smallest of offices Bell did want automatic switching
since volume didn't justify having an operator on duty 24/7. But SxS
wasn't up to the task in its earliest days. (Later a "community dial
office" was specially developed and was a very popular offering.)
Bell and Automatic Electric agreed to share patents and Bell had AE
build switch units for it for many years.
I believe at its peak SxS handled 49% of the lines in the Bell
System. Interestingly, step was still strongly represented in the
late 1970s (both in central office and PBX) despite its limitations
and costs in handling DDD and Touch Tone*. But common control was
still very expensive and only cost-justified in large high volume
offices. Further, while SxS needed more routine maintenance than
later units, the skill and debugging level was relatively easy as
compared to crossbar which required more sophisticated training for
the staff.
*For some reason, early step reversed polarity upon a connection.
This would screw up early Touch Tone phones which were polarity
sensitive (the tone pad). They had to change that. Also, adding a
Touch Tone receiver front end to a step office was cumbersome and
expensive, too. Bell found low-cost units that worked on PBXs weren't
good enough for CO use. (Hard for us today to think about that kind
of thing; we're so spoiled by high-grade electronics.)
The Bell System histories provide a good source of information for the
above. Old "Bell Laboratory Record" magazines would be great to
read. They're usually found in large urban or college library
archives and require a request. If you're lucky enough to find an old
set in open stacks, sit down and spread out and go through a bunch of
them--fascinating!