Aug 12, 2009, 1:43:09 PM8/12/09
Hello, and thanks for reading this. I'm the moderator of The Telecom
Digest: for those who havne't read it before, it's an online e-zine
that appears on Usenet as comp.dcom.telecom. I've Just joined the
group, and I hope I'll be able to contribute a lot, but my first post
is one asking for your help.
This is an unusual question, so please bear with me.
Once of the Digest's readers has asked for help interfacing a "Local
Battery/Local Magneto" PBX with the PSTN, and I'm trying to think
"outside the cubicle", and come up with a solution that doesn't
require spending a lot of money.
Here's the situation: there's a rustic vacation setting in Verizon
territory, where every cabin has an honest-to-god wall phone with a
magneto crank on the side and a battery in it to power the
microphone. Yes, pretty much every image of Ma & Pa Kettle applies.
The cabins are connected to a central cord board, which is, literally,
the telephone exchange for every building on the property, and which
_also_ has a magneto and batteries for the operator's headset: just
imagine a 555 board with a magneto on the side (in fact, that used to
be an option for 555 boards). The cabins signal the operator with the
magneto, by cranking the handle when they want to talk to another
cabin or the office, the restaurant, etc. The operator does the same
for calls between the cabins (or restaurant, etc.), i.e., (s)he cranks
the magneto on the switchboard to ring the phone at the destination
phone. After a call is completed, one of the stations "rings off",
i.e., cranks the magneto to activate the "drop" flag on the operator's
console, so that the operator knows it's time to disconnect.
Now, you're probably wondering why anyone would use such a setup, but
AFAIK this is a real place, and the equipment is really there and in
use every day. The Telecom Digest reader I'm trying to help says the
strongly that the "crank" phones add a distinctive charm to the cabins
and create an "old timey" atmosphere which is good for business, so
they are determined to keep the existing equipment. However, they need
to be able to route calls from the outside world to their cabins, and
want to be able to originate calls from them, so my reader asked for
help in finding out what's possible.
Ergo, I have these questions, and I'd like to hear from Central Office
technicians and engineers.
1. Are central office dial tone circuits capable of accepting ring
signals from a magneto PBX? In other words, if the PBX in question
is attached to a dial tone "trunk", and the operator cranks the
magneto, is the CO capable of connecting the call to a Verizon
operator? (I know this *can* be done, because I once accidentally
cranked a magneto on a surplus field phone that was connected to a
dial tone line, and an operator answered, but the question is if it
is a regular feature of common central office equipment.)
2. Are the CO's Verizon uses capable of supporting "Ring down" trunks?
Assuming that an ordinary "PBX trunk", i.e., a dial tone line,
can't work on a ring-down basis, could Verizon option a circuit
so that it can be done? I'm thinking of "manual service" lines used
by paraplegics and others who can't dial a call.
3. Assuming that options 1 or 2 aren't available, what "work around"
is available that would allow the 555 PBX to interface with the
PSTN despite it's lack of DC supervision and the need to use
Thanks for your help.