Author Topic: Question on Subscriber Plug/Jack Assembly  (Read 249 times)

Offline Desert Phone Guy

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Question on Subscriber Plug/Jack Assembly
« on: September 20, 2018, 12:43:17 PM »
I recently picked up this jack and plug set.  The plug is marked 278A and the jack is marked 389A.  I had one of these years ago and I was told then that these were the predecessor of the 4-prong jack for residential service.  They are made of metal, the jack being steel, and the plug has a brass painted black housing.

I would like to know the timeline of when these were manufactured and used.  Photos are attached.

Thanks for any help.

Offline poplar1

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Re: Question on Subscriber Plug/Jack Assembly
« Reply #1 on: September 20, 2018, 02:51:22 PM »
4-prong plugs and jacks were necessary for portable anti-sidetone sets such as 151AL and 202.
This 1932 BSP -- C36.201 issue 1 -- shows 3-, 4- and 8-conductor jacks and plugs: The 8-conductor was for the 205 multi-line set.

bsp-bell-system-practices -- c33-c38-dials-transmitters-receivers-cords/4597-c36-201-i1-feb32-jacks-plugs-inside-loc

(TCI Library)
« Last Edit: September 20, 2018, 04:11:23 PM by TelePlay »
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline Haf

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Offline Desert Phone Guy

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Re: Question on Subscriber Plug/Jack Assembly
« Reply #3 on: September 20, 2018, 03:14:53 PM »
Wow!  Thanks for the great information, accurate and quick!! 

So, this being from the early 1930's, and having only 3 conductors, would it have been used with say a 51AL dial stick, or an early 302 desk set perhaps?

Offline Haf

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Re: Question on Subscriber Plug/Jack Assembly
« Reply #4 on: September 20, 2018, 03:17:35 PM »
Everything not anti sidetone with an for e.g. 534 A  or 584 A sidetone subset where only three conductors needed.

Haf
Telephone:
0049-030-55474418
1-415-449-4743
1-604-757-7474