Author Topic: Tip Ring And Ground  (Read 2532 times)

Offline dsk

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Tip Ring And Ground
« on: August 25, 2009, 03:00:52 PM »
As I understand You used a similar system as Norway with the ringer between Tip and Ground on some older installations.

In Norway we have no tradition of a demarcation  point. The tel-co was running the line too the first outlet. (Actually they had a monopoly, and you could do noting by youselves.)   The typical old Norwegian outlet and plug is at the picture.

The American outlets had 4 pins, why?


Offline Phonesrfun

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Re: Tip Ring And Ground
« Reply #1 on: August 25, 2009, 03:31:43 PM »
I believe the original 4-prong plug in the US came about and dates back to the days of a separate telephone from the subset where the ringer, induction coil and the condenser were contained in the subset.  All the telephone consisted of was a transmitter and receiver with the hookswitch and a dial if it were dial service.  For anti sidetone service, 4 wires are needed between the subset and the telephone.

A WE 202 deskstand or a WE 151AL candlestick would have been such installations.  I have seen old movies where a 202, for instance, was used in a restaurant, and conveniently plugged in to a plug next to a customer's booth for them to use the phone.  Obviously, they would not want to carry the subset around, but just the phone itself.

The wire colors WE used between the phone and the subset in the desk stand wire were red, green, yellow, and black.  This color scheme matches the colors used on the old 4-prong plug and, indeed carry over to a great extent even today.

I believe when the self contained phone was developed in the case of the 302, there was no need to reinvent the plug.  They just used the same plug, but only two wires (tip and ring) for private line use, and added the ground wire for grounded divided party line ringing.

also in the old days, the phone company here also owned the wiring that was inside the house.  The demarc used today is mostly a result of the breakup of the phone companies, where the dividing line between "yours and mine" needed to be made.  Prior to that, it was not supposed to be permitted for the home owner to even touch the phone company's wire.  Although that was the written rule, it was widely known that people connected their own devices to the phone company wires all the time.  All the more need for a demarcation.

Before the use of the formal demarcation, there was usually a protective grounding block mounted right where the outside or overhead drop entered the premises.  This was for lightning protection and/or protection in case a power line were to have fallen on the phone wire.  Many of those terminal blocks still remain in place today.

-Bill G