[sci.electronics] telephone systems

esmonddp@jupiter.crd.ge.com (Daniel P. Esmond) (12/29/89)

HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!

Last night I went to change a phone jack from a four pronger to a
modular, in the house that I rent. Opening the old outlet I found 
two sets of wires feeding to the outlet (not unusual), and proceeded
to change the plate. Touching a wire I recieved a HV shock which 
didn't surprise me, but what did surprise me is that the other
phones in the house didn't ring the same time I received the shock.
Grabbing my meter I tested the line, and sure enough there is a
constant 120 volts on the green wire. Being curious I began to trace
the wires throughout the house and found that all the outlets were
wired daisy chain fashion, and there is an AC transformer in the
loop. The secondary is only 16 volts, so trying to locate the
source of the high potential I disconnected the main line from the
loop. The loop went dead, and the main line still had 120 volts
open circuit coming into the house.

Do all phone lines feed 120 volts constant?
What is the transformer for?
Why are all the phones daisy chained instead of parallel?

I don't want to smoke a brand new $200 phone and answering combo,
but I do want to get this hooked up as soon as possible (hopefully
tonight). I thought phone lines ran a low voltage trickle and rang
the line with about 75 volts. What could the constant 120 volts be
for? Will it damage my stuff?

Thanks!Thanks!Thanks!Thanks!Thanks!Thanks!Thanks!Thanks!Thanks!

- Dan

esmond@crd.ge.com

peg@psuecl.bitnet (PAUL E. GANTER) (12/29/89)

In article <4370@crdgw1.crd.ge.com>, esmonddp@jupiter.crd.ge.com (Daniel P. Esmond) writes:
> HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!HELP!
>
> Grabbing my meter I tested the line, and sure enough there is a
> constant 120 volts on the green wire. Being curious I began to trace
> the wires throughout the house and found that all the outlets were
> wired daisy chain fashion, and there is an AC transformer in the
> loop. The secondary is only 16 volts, so trying to locate the
> source of the high potential I disconnected the main line from the
> loop. The loop went dead, and the main line still had 120 volts
> open circuit coming into the house.
>
> Do all phone lines feed 120 volts constant?
> What is the transformer for?
> Why are all the phones daisy chained instead of parallel?

Sounds like some very weird things were done in this house!  The
transformer you describe was probably used to power dial lights for
several phones in the house.  A lot of those were recalled for being
fire hazards--you should probably trash it immediately!!  It might be
shorted, thus putting 120 VAC on the old 16 VAC line.  As for the
normal (two-wire) line, it certainly shouldn't be daisy-chained--in
fact, I don't see how the phones could work if it is.

My proposed solution:  trash the transformer and check again.  If
120 VAC still there you should probably let your landlord and the
phone company figure it out--if things are that screwed they should
probably be rewired!!

Good luck!

Paul

hbg6@citek.UUCP (John Schuch) (12/30/89)

In article <4370@crdgw1.crd.ge.com> esmonddp@jupiter.crd.ge.com (Daniel P. Esmond) writes:
>Grabbing my meter I tested the line, and sure enough there is a
>constant 120 volts on the green wire. Being curious I began to trace
>.......
>wired daisy chain fashion, and there is an AC transformer in the
>loop. The secondary is only 16 volts, so trying to locate the
>
>- Dan


The 16Vac transformer usually drives the LEDs which light up the dial
on 'trim line' style phones. If you don't have those phones, possibly
someone else did and left the transformer. I usually remove it and toss
it into my shop junk box ( I'll find a use for them SOME day :-) ).

I also had a brief problem with HVac on a phone line but it went away
when the phone company swung the wires over to the next pole so than
the phone wires were not parallel to the 440Vac power lines into the
shop. We toasted two modems before we figured it out.

[John]