Why 4-wire and 2-wire telephone cable?
Hanford Chan
Hi,
Excuse me, I have a question about the telephone wiring. There are
two kinds of cables from the telephone set to the socket. One is 4-wire
and another is 2-wire. I want to ask, specifically, what are the 4 wires
and 2 wires for? Are 2 wires enough? Why are there two standards?
Another question is that in my city the modular plug for the phone set
and that for the socket is different: The modular plug for the telephone
set is the same as that for modem: square-shaped and transaprent. The
plug for the socket is rectangular-shaped and opaque. I have been told
that the former is in US standard and the latter is in UK standard. Is
that right?
I don't know if I have posted in a wrong newsgroup. Sorry for the
disturbance.
Rgds,
Hanford Chan
--
Chan Hang Fung Hanford | Email : hfc...@ie.cuhk.edu.hk
Department of Information Engineering | Office: (852) 2609-8353
The Chinese University of Hong Kong | Fax : (852) 2603-5032
Garry Lee
The other 2 wires are for power supply in the case of digital line.
Jay R. Ashworth
Garry Lee (garr...@singnet.com.sg) wrote:
: Hanford Chan wrote:
: > Excuse me, I have a question about the telephone wiring. There are
: > two kinds of cables from the telephone set to the socket. One is 4-wire
: > and another is 2-wire. I want to ask, specifically, what are the 4 wires
: > and 2 wires for? Are 2 wires enough? Why are there two standards?
: > Another question is that in my city the modular plug for the phone set
: > and that for the socket is different: The modular plug for the telephone
: > set is the same as that for modem: square-shaped and transaprent. The
: > plug for the socket is rectangular-shaped and opaque. I have been told
: > that the former is in US standard and the latter is in UK standard. Is
: > that right?
: The other 2 wires are for power supply in the case of digital line.
Among other things. In the US, those second pair of wires is also used
for a second line, in an RJ-14 wiring system, and you occasionally see
a third pair, the RJ code for which I forget.
Another use is for the A-A1 pair whenn conecting a single line phone to
an older electro-mechanical key system; this is called an RJ-12.
Cheers,
-- jra
--
Jay R. Ashworth j...@scfn.thpl.lib.fl.us
Member of the Technical Staff Unsolicited Commercial Emailers Sued
The Suncoast Freenet Pedantry: It's not just a job, it's an adventure.
Tampa Bay, Florida +1 813 790 7592
dcr...@bellsouth.net
hfchan5@bansun07 (Hanford Chan) wrote:
>Hi,
> Excuse me, I have a question about the telephone wiring. There are
>two kinds of cables from the telephone set to the socket. One is 4-wire
>and another is 2-wire. I want to ask, specifically, what are the 4 wires
>and 2 wires for? Are 2 wires enough? Why are there two standards?
>Another question is that in my city the modular plug for the phone set
>and that for the socket is different: The modular plug for the telephone
>set is the same as that for modem: square-shaped and transaprent. The
>plug for the socket is rectangular-shaped and opaque. I have been told
>that the former is in US standard and the latter is in UK standard. Is
>that right?
> I don't know if I have posted in a wrong newsgroup. Sorry for the
>disturbance.
>Rgds,
>Hanford Chan
>--
>Chan Hang Fung Hanford | Email : hfc...@ie.cuhk.edu.hk
>Department of Information Engineering | Office: (852) 2609-8353
>The Chinese University of Hong Kong | Fax : (852) 2603-5032
Actually what got it all started was a few years ago, about thirty, a
new item was introduced, the lighted telephone set. This was before
leds were in mass use. Power was needed for the light bulb in the
handset so an AC/DC power supply was added to the line usually on the
yellow/black pair so 12volts dc could power lights,also if an outside
bell was to be used the signal for it could be sent on this extra pair
of wires.
The normal telephone line just takes the two wires, one battery the
other ground, therefore when you lift the handset there is a short
placed on the line and a complete path is formed for the battery to
flow on till it gets to ground.. Old telephone saying used here is "
battery hunting ground" Maybe this will clarify somethings ,but as
others have said the most common use today is a second line.
Mitch Thompson
On 27-Mar-97 02:06:48 dcrews posted a message in comp.dcom.telecom.tech
concerning Re: Why 4-wire and 2-wire telephone cable?, in which it was stated:
>hfchan5@bansun07 (Hanford Chan) wrote:
>>Hi,
>> Excuse me, I have a question about the telephone wiring. There are
>>two kinds of cables from the telephone set to the socket. One is 4-wire
>>and another is 2-wire. I want to ask, specifically, what are the 4 wires
>>and 2 wires for? Are 2 wires enough? Why are there two standards?
>>Another question is that in my city the modular plug for the phone set
>>and that for the socket is different: The modular plug for the telephone
>>set is the same as that for modem: square-shaped and transaprent. The
>>plug for the socket is rectangular-shaped and opaque. I have been told
>>that the former is in US standard and the latter is in UK standard. Is
>>that right?
>> I don't know if I have posted in a wrong newsgroup. Sorry for the
>>disturbance.
>Actually what got it all started was a few years ago, about thirty, a
>new item was introduced, the lighted telephone set. This was before
>leds were in mass use. Power was needed for the light bulb in the
>handset so an AC/DC power supply was added to the line usually on the
>yellow/black pair so 12volts dc could power lights,also if an outside
>bell was to be used the signal for it could be sent on this extra pair
>of wires.
>The normal telephone line just takes the two wires, one battery the
>other ground, therefore when you lift the handset there is a short
>placed on the line and a complete path is formed for the battery to
>flow on till it gets to ground.. Old telephone saying used here is "
>battery hunting ground" Maybe this will clarify somethings ,but as
>others have said the most common use today is a second line.
Interesting...I was under the impression that the Red/Green pair was line one,
the Yellow/Black pair was line two. Why supply power this way, when the power
to light your telephone set from the office battery?
However the old military AUTOVON telephone system used all 4 wires (T/R,
T1/R1) as independent talk and listen paths.
Then again, April 1 /is/ just around the corner. ;^)
--
Mitch Thompson, San Antonio, TX WB5UZG
My PGP key Fingerprint: B7 BA 0C EF AC CD FD FE EC F3 14 AE 04 94 18 A3
To receive my Public Key, send an email to me with "REQUEST PGPKEY" as
the subject. Feel free to send your Public key in the BODY of the email.
Some lead. Others follow. I'm lost.
GreivAngel
The Red/green pair and the black/yellow pair are two sepperate lines. This
is just idle speculation... but wouldn't the load on the line be too great
if just one line had to power the communication circut and the light?
Garry Manning
GreivAngel <greiv...@aol.com> wrote in article
<19970331045...@ladder01.news.aol.com>...
The original post was interesting. I've never seen two wire telephone
cable. The smallest I've seen is two pair ( 4 wire).
Erik H. Bakke
Garry Manning <mann...@netcom.ca> wrote in article
<01bc3f66$96de5ae0$4252b5cf@username_rem.software.mitel.com>...
>
> > The Red/green pair and the black/yellow pair are two sepperate lines.
> This
> > is just idle speculation... but wouldn't the load on the line be too
> great
> > if just one line had to power the communication circut and the light?
> >
> The original post was interesting. I've never seen two wire telephone
> cable. The smallest I've seen is two pair ( 4 wire).
>
years. Only the few last years, 2 pair and 4 pair cabling has become more
common.
I have seen several examples of telephone cabling being marketed as ISDN
ready just because they use RJ45 connectors in the end, but there were
still only 2 wires in the cable.
---
Erik h. Bakke
er...@megafon.no
eri...@bgnett.no
Frank Pitt
In article <5gt5q9$a...@eng-ser1.erg.cuhk.edu.hk> hfchan5@bansun07 writes:
>
>Hi,
>
> Excuse me, I have a question about the telephone wiring. There are
>two kinds of cables from the telephone set to the socket. One is 4-wire
>and another is 2-wire. I want to ask, specifically, what are the 4 wires
>and 2 wires for? Are 2 wires enough? Why are there two standards?
Older (mainly rotary) phones contained the ballast(?) capacitor in them,
rather than in the socket. It was neccessary to pass the ring tone onto
the phone.
If you had an extension phone, and wanted the extension to ring as well,
you needed four wires to your extension jack as well.
>Another question is that in my city the modular plug for the phone set
>and that for the socket is different: The modular plug for the telephone
>set is the same as that for modem: square-shaped and transaprent. The
>plug for the socket is rectangular-shaped and opaque. I have been told
>that the former is in US standard and the latter is in UK standard. Is
>that right?
Yes.
Hong Kong, being a British colony until recently probably uses
the BT wall socket.
The RJ12 on the phone and modem is because BT never liked
having "plugs" on the phones, initially they were all spade
terminals inside the phone.
I still have a "BT jack adaptor" that adapts the old
hardwired telephone with spade terminals on both ends
so that you can plug it into a BT socket.
My house in Christchurch, NZ, only went to BT sockets
when I rewired it myself ( against the law at the time :-) )
in about 1987, removing the hard wired terminal and adapting
the rotary phones so I could plug in my state of the art
2400 baud modem.
Frankie
Jay R. Ashworth
Garry Manning (mann...@netcom.ca) wrote:
: GreivAngel <greiv...@aol.com> wrote in article
: <19970331045...@ladder01.news.aol.com>...
: > The Red/green pair and the black/yellow pair are two sepperate lines.
: This
: > is just idle speculation... but wouldn't the load on the line be too
: great
: > if just one line had to power the communication circut and the light?
: >
: The original post was interesting. I've never seen two wire telephone
: cable. The smallest I've seen is two pair ( 4 wire).
Yup. There are several manufacturers who ship 2-wire RJ-11 cords with
their gear, which really screws those of us who only need 1 line of
answering machine in front of our 2 line phone. Of course, most of the
_answering machines_ don't pass the extra pair any... _EVEN_ my AT&T...
which also _comes_ in a 2-line version.
<sigh>
Cheers,
-- j
Robert Becnel
dcr...@bellsouth.net wrote:
: hfchan5@bansun07 (Hanford Chan) wrote:
: >Hi,
: > Excuse me, I have a question about the telephone wiring. There are
: >two kinds of cables from the telephone set to the socket. One is 4-wire
: >and another is 2-wire. I want to ask, specifically, what are the 4 wires
: >and 2 wires for? Are 2 wires enough? Why are there two standards?
: >Another question is that in my city the modular plug for the phone set
: >and that for the socket is different: The modular plug for the telephone
: >set is the same as that for modem: square-shaped and transaprent. The
: >plug for the socket is rectangular-shaped and opaque. I have been told
: >that the former is in US standard and the latter is in UK standard. Is
: >that right?
: > I don't know if I have posted in a wrong newsgroup. Sorry for the
: >disturbance.
: >Rgds,
: >Hanford Chan
: >--
: >Chan Hang Fung Hanford | Email : hfc...@ie.cuhk.edu.hk
: >Department of Information Engineering | Office: (852) 2609-8353
: >The Chinese University of Hong Kong | Fax : (852) 2603-5032
: Actually what got it all started was a few years ago, about thirty, a
: new item was introduced, the lighted telephone set. This was before
: leds were in mass use. Power was needed for the light bulb in the
: handset so an AC/DC power supply was added to the line usually on the
You mean DC only don't you? I don't think you would want to mix 120VAC
on the same line as -48/48 V DC.
Bob
--
**************************************************************************
Robert G. Becnel bec...@crl.com (email) http://www.crl.com/~becnel (www)
**************************************************************************
Robert Casey
>: > Excuse me, I have a question about the telephone wiring. There are
>: >two kinds of cables from the telephone set to the socket. One is 4-wire
>: >and another is 2-wire. I want to ask, specifically, what are the 4 wires
>: >and 2 wires for? Are 2 wires enough? Why are there two standards?
>: >Another question is that in my city the modular plug for the phone set
>: >and that for the socket is different: The modular plug for the telephone
>: >set is the same as that for modem: square-shaped and transaprent. The
>: >plug for the socket is rectangular-shaped and opaque. I have been told
>: >that the former is in US standard and the latter is in UK standard. Is
>: >that right?
>
>: new item was introduced, the lighted telephone set. This was before
>: leds were in mass use. Power was needed for the light bulb in the
>: handset so an AC/DC power supply was added to the line usually on the
>
>You mean DC only don't you? I don't think you would want to mix 120VAC
>on the same line as -48/48 V DC.
>
secondary to allow connection of the extra pair of wires to drive the
light bulb in the phone. Something like 12V AC was used. The transformer
could be remotely located anywhere where the 4 wire phone cable and
a powerline was avaliable.
I think the phone company (AT&T back in the olden days) figured that the
cost of installing the phone cable was a lot more than the cost of the wire,
and the incremental cost of providing a spare pair was neglectable compared
to the labor costs.
Don Ritchie
Robert Casey (wa2...@netcom.com) wrote:
: >: > Excuse me, I have a question about the telephone wiring. There are
And there were transformers that were 10VAC and 18VAC that looked the
same. If you put in a 18VAC transformer you would be back in a few days to
replace the 10V bulb in the set. You could rreplace the bulb with a 24V
bulb or put in another 10V bulb and replace the transformer.
--
-
Free advice is worth every penny you paid for it !
Don Ritchie Century Communications Euclid, Ohio
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Christoper W. (Chris) Boone
Robert Becnel wrote:
>
> dcr...@bellsouth.net wrote:
> : Actually what got it all started was a few years ago, about thirty, a
> : new item was introduced, the lighted telephone set. This was before
> : leds were in mass use. Power was needed for the light bulb in the
> : handset so an AC/DC power supply was added to the line usually on the
>
> You mean DC only don't you? I don't think you would want to mix 120VAC
> on the same line as -48/48 V DC.
>
>
AHHH how do you think they RING the phone???????? or turn on the msg
waiting lamp??? If the phone is NOT offhook, BOTH AC and DC can appear on
the line at the same time....and do everytime the phone rings..
Chris
Christoper W. (Chris) Boone
Garry Lee wrote:
>
> The other 2 wires are for power supply in the case of digital line.
EEEAAAHHHH!!! Wrong.....Digital phones use TWO wires...not 4...in the
case of PBXs, Nortel and ROLM supply DC over the same cable that
supplies the digital signal to the phone... 4wire cable is used in some
Key systems and hybrids to supply separate lines for AUDIO and CONTROL...
ISDN and T1s use two pairs...one pair for TX, the other for RX...
And in analog residential cabling, the second pair is used for 2nd phone
line or AC power for phone lamp...
Chris
Don Ritchie
Christoper W. (Chris) Boone (cbo...@earthlink.net) wrote:
You know Chris, It wouldn't be so bad if all the people that don't know
what they are talking about, didn't do it with so much authorty. :-)
Don
David Clayton
"Christoper W. (Chris) Boone" <cbo...@earthlink.net> contributed the
following:
>Garry Lee wrote:
>>
>> The other 2 wires are for power supply in the case of digital line.
>
>EEEAAAHHHH!!! Wrong.....Digital phones use TWO wires...not 4...in the
>case of PBXs, Nortel and ROLM supply DC over the same cable that
>supplies the digital signal to the phone
>....
Some PBX's use 2 wires for digital phones, some use 4 wires.
Regards, David.
---------------
**Remove the second "@" from the 'Reply To' (spam reducer!)**
David Clayton, e-mail: dcs...@acslink.aone.net.au
Melbourne, Victoria, Australia.
"Virtual Reality - Give it a rest, Actual Reality has me stressed enough as it is."
Garry Manning
Jay R. Ashworth <j...@scfn.thpl.lib.fl.us> wrote in article
<5hunin$4pq$3...@news.usf.edu>...
> I have seen station line cords that are only two wire but no station
cabling that is two wire.
Michael Wright
drit...@nacs.net (Don Ritchie) wrote:
>: EEEAAAHHHH!!! Wrong.....Digital phones use TWO wires...not 4...
Not! Many digital systems use multiple pairs - AT&T Legend, for examp.
>in the
>: case of PBXs, Nortel and ROLM supply DC over the same cable that
>: supplies the digital signal to the phone... 4wire cable is used in some
>: Key systems and hybrids to supply separate lines for AUDIO and CONTROL...
In MOST keys and hybrids. AT&T Partner's blue pair works a T/R device,
orange pair kicks the cpu to system-phone mode.
>: ISDN and T1s use two pairs...one pair for TX, the other for RX...
May I introduce you to someone who doesn't do much ISDN work! ISDN is
a SINGLE-pair facility. T-1 is two pair.
>: And in analog residential cabling, the second pair is used for 2nd phone
>: line or AC power for phone lamp...
>:
>: Chris
The second pair is there because no one makes 1-pair cable for
telephony.
Michael
VoiceX
1-888-2-Voice-X
Scott Shattles
>Chris
Chris
They turn on msg waiting lamps using FSK (freguency shift key)
modulation, also known as message waiting illumination. this is the
same signaling used to send caller i.d data
Scott Shattles
scottp
Thank you mike for smacking that dude around
He needs to go out and work and learn something or get a new job.
On Tue, 08 Apr 1997 13:29:11 GMT, v...@telalink.net (Michael Wright)
wrote:
Don Ritchie
Scott Shattles (shat...@mindspring.com) wrote:
Here we go again !!! none of this has ANYTHING to do with the orig. post.
Just to keep it stright. The lamps on the "old" lighted phones were
18VAC, I'll say that one more time A.C. The bulbs were (are?) 52A lamps.
( not to be confuesed with 10V, 51A lamps, used in 1A1 & 1A2 Key systems)
Also, for that "someone" that just has to make the point, YES I (we) know
that the lamps WILL work with D.C. just 99% of the time AC was used.
Now to answer Scott, FSK message wait lights are new, The "old' ( and
still often used) way of lighting MW lights, Rev. polarty 90V DC on the
line. The dead giveaway, if the MW lamp "flashes" on ringing, it is most
likely a 90v neon that lights on 90V ( ac or dc ) If not it's light by
FSK.
Don Ritchie
Steve Lucius
:
:
: >: ISDN and T1s use two pairs...one pair for TX, the other for RX...
:
: May I introduce you to someone who doesn't do much ISDN work! ISDN is
: a SINGLE-pair facility. T-1 is two pair.
:
:
Actually ISDN can be a two wire or four wire interface. In BRI the "U" interface
which is typically used from central office to customer premise is a 2 wire
interface good for about 19,000 feet. This is then often terminated in a NT1
which converts it to a 4 wire interface good for about 1000 feet (and "S" or "T" interface). PBX implementations of BRI can produce either the long distance "U" interface or the local
"S/T" interface. Some customer premise equipment requires an "S" interface some a "U". The T1 (or E1) based PRI requires 4 wires. The answer to the question "does ISDN require a 2 or 4 wire connection" is yes.
John Lundgren
scottp (sco...@mindspring.com) wrote:
: Thank you mike for smacking that dude around
: On Tue, 08 Apr 1997 13:29:11 GMT, v...@telalink.net (Michael Wright)
: wrote:
: >drit...@nacs.net (Don Ritchie) wrote:
: >
: >
: >>: EEEAAAHHHH!!! Wrong.....Digital phones use TWO wires...not 4...
: >
: >Not! Many digital systems use multiple pairs - AT&T Legend, for examp.
: >
: >
: >>in the
: >>: case of PBXs, Nortel and ROLM supply DC over the same cable that
: >>: supplies the digital signal to the phone... 4wire cable is used in some
: >>: Key systems and hybrids to supply separate lines for AUDIO and CONTROL...
: >
: >
: >In MOST keys and hybrids. AT&T Partner's blue pair works a T/R device,
: >orange pair kicks the cpu to system-phone mode.
: >
: >
: >>: ISDN and T1s use two pairs...one pair for TX, the other for RX...
: >
: >May I introduce you to someone who doesn't do much ISDN work! ISDN is
: >a SINGLE-pair facility. T-1 is two pair.
ISDN is a single pair from the CO to the dwelling, but after it gets
there, it can change to two pair. I forget what they call it, but you can
find out all about ISDN at Pac Bell's web page.
I'm guessing www.pacbell.net.
: >
: >
: >>: And in analog residential cabling, the second pair is used for 2nd phone
: >>: line or AC power for phone lamp...
: >>:
: >>: Chris
: >
: >The second pair is there because no one makes 1-pair cable for
: >telephony.
: >
: >Michael
: >VoiceX
: >1-888-2-Voice-X
--
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