Author Topic: Wiring  (Read 1019 times)

Offline ntophones

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Wiring
« on: October 28, 2009, 11:53:37 AM »
Hello,
Are the wires coming in from the wall just positive and negative? Where does a ground for a land line phone come from?
What happens if you hook the wires from the wall into the phone backwards?
Thanks.
nto
--nto

Offline Phonesrfun

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Re: Wiring
« Reply #1 on: October 28, 2009, 01:07:19 PM »
Phone wires from the wall are positive and negative, but they are both isolated from ground.  In the olden days, when there was party line ringing,  the ringing current would often go between one side of the line and ground to achieve selective ringing.  Now, with no party lines, ringing is just sent down the line and not referenced to ground.  When ground was used, it was necessary to use a third wire, which was grounded to a grounding source in the house or business, like a water pipe or a grounding rod.  These just are not used any more, so when you see a phone line, you are just looking at positive and negative without any reference to ground.

To answer your second question as to what if you hook the phone up backwards.  The world comes to an abrupt end.  No, not really.  Older dial telephones have no polarity sensitive components, so there is no problem with hooking one of those up "backwards", because there was no such thing as backwards.  However, if the phone was once set up for party line ringing, failure to get the grounding right could have once caused a phone to ring when your neighbor's phone was supposed to be ringing.  Like I mentioned, that is simply not the case any more.

Touch-tone phones do contain polarity sensitive components.  Namely transistors and in later cases a "chip".  When Ma Bell first came out with touch tone, only Bell System installers were allowed to install phones, and they knew how to install with the correct polarity.  If the phone was hooked up in reverse, everything except for the touch-tone dial would work, because except for the dial, the rest of a touch tone phone was exactly the same as an older dial phone.

When the phone company started selling phones to the general public, and anyone was allowed to hook up phones, the phone company knew that there was a 50% chance that someone would hook the phone up correctly and 50% would not.  So, at that point, they began putting a polarity guard in the touch-tone dial circuit so that any dummy could hook up a touch-tone phone.

As collectors, we sometimes get older hard-wired touch tone phones.  Therefore, we need to be the installer that is familiar with polarity.  Good rule of thumb is if you hook up a touch tone phone and it fails to make tones, then simply reverse the line, and it should.

All the newer all electronic phones and cordless phones have built-in polarity guards, so there should be no problems.

One other thing.  Sometimes it was necessary to reverse the polarity if a bell would clap a little and make little tinkling noises when operating a rotary pulse dial.  This apparent polarity sensitivity was caused by the charging of the ringer capacitor, and while technically is a polarity issue, it was not critical to the operation of the phone.

Probably one of the things that haunts the beginner phone collector more than anything else is getting around the issue of phones that were once designed for party ringing, where one side of the ringing was designed to go to ground.  It is a simple fix, but one that varies from phone to phone, so we seem to see a lot of requests for help in getting an old phone to ring.

-Bill G

Offline ntophones

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Re: Wiring
« Reply #2 on: October 28, 2009, 02:05:25 PM »
Thank you so much for that fascinating read! I am so thankful to you guys!
That answered so many questions.
nto
--nto

Offline Dan

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Re: Wiring
« Reply #3 on: October 28, 2009, 07:01:45 PM »
Good info, Bill.  ,If you have a specific phone ,ntophones, we can get it to ring for you.
« Last Edit: October 28, 2009, 07:17:59 PM by Dan »
"Imagine how weird telephones would look if our ears weren't so close to our mouths." - Steven Wright

Offline ntophones

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Re: Wiring
« Reply #4 on: October 28, 2009, 07:15:24 PM »
It's my AE40--I'm the one with the funny hang up problems....However, I talked to someone who said that my condenser was probably leaking, so I'm getting a new one. If it still has problems, I'll have to change out some more parts.
I tell you, though, everyone here is so nice to help me.
I've been trying to get my little phone to work right with the period parts for a long time.
I think when I've gotten it to work correctly, I'll have a picture party here! =).
But, if I need more help (which I probably will), I'll let you guys know...
I've learned many interesting things, however. I can't wait to get it to work and try out my skills on another phone!
nto
--nto