Author Topic: Western Electric 51C desk stand with 554C subset  (Read 3742 times)

unbeldi

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Western Electric 51C desk stand with 554C subset
« on: July 26, 2014, 08:07:39 PM »
The 51C desk stand is a variation of the No.51 candlestick and was only used on two-party subscriber lines for message rate service. For this service, the central office had to automatically identify the station that originated a call and bill the responsible party. For this purpose, the desk stands for both parties, the tip-party and the ring-party on the line were equipped with 554-C subscriber sets. The specific wiring and switching in the device distinguished the parties. When a caller removed a receiver to place a call, the tip-party station connected a 1000 Ω resistance, furnished by the ringer coils, between the line and ground, while the ring-party did not.

The tip-party station equipment was distinguished with the part designation "C", while the ring-party station was a standard 51AL or equivalent instrument.

Previously, the 50C candlestick served the same purpose, but the 51C had additional terminal plates (R,GN and RR,B) for connecting the mounting cord. Later, the 51C was replaced by the 103-type telephone based on either an A2, or B2 (before 1930) or a D2 (since 1930) handset mounting, which were desk top-style handset telephones.

The 51C/554C telephone was still a sidetone instrument. Starting in ca. 1931, these could be upgraded to the anti-sidetone version, which was the 151C desk stand. The 151C used a 634-BC or a 684-BC subset.

The 554C subset is similar in construction to the 534-type device, a pressed metal enclosure with enclosed gongs, but it has two condensers, instead of one. The desk stand is connected by a five-conductor mounting cord. The dial shown in the diagrams is a 2A dial, which has four terminals, Y, BK, BB, and W, implementing the dial pulse switch between Y and BK, and a break-make switch of BB between BK, and W.

Diagrams
  • Circuit diagram drawn based on C63.374 i3 (1945)
  • Wiring diagram from C63.374 i3 (1945) enhanced with line color
  • Wiring diagram from AT&T Spec 4566 (1926)

Use for party on ring
The telephone set for the ring party on a two-party message rate line may be a standard 51AL with a 554C subset. However, for simplicity of management, both stations on the line may have received the same 51C, the ring party being rewired as follows (C46.101):
  • Move red ringer wire from B to RR
  • Move yellow ringing condenser wire from L1 to L2Y

Wiring on modern telephone lines (bridged ringing)
  • Move black ringer wire from GND to L2
  • Move red ringer wire from B to RR
This connects the ringer permanently in series with the ringing capacitor across the telephone line (L1, L2), while preventing an off-hook DC shunt by the ringer across the transmitter and dial pulse switch, which may cause trouble when dialing.

References
  • AT&T Specification 4566, February 1926, p.66 (51-C) and p.67 (50-C)
  • BSP Section C63.374, Issue 1 (3-2-36), ibid. Issue 3 (6-28-45)
  • BSP Section C46.101, Issue 1 (1-6-32), Sidetone Line and Ringer Connections - Common Battery Main Stations
« Last Edit: February 17, 2015, 05:45:15 PM by unbeldi »

unbeldi

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Re: Western Electric 51C desk stand with 554C subset
« Reply #1 on: July 27, 2014, 09:15:42 PM »
This is a view of the wiring of a 51C desk stand that was refurbished in March 1933, including the original 554C as found.

The two phenol terminal plates with connections RR and B (left) and R and GN (right) are clearly visible.

Cord set: D5A, D5B, T1A, R2A
Dial: 2AB
« Last Edit: July 26, 2015, 11:03:12 PM by unbeldi »

unbeldi

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Re: Western Electric 51C desk stand with 554C subset
« Reply #2 on: February 16, 2015, 03:57:35 PM »
The second telephone on a two-party line with message rate accounting was the 51AL desk stand. It served the ring side of the line, while the 51C was the tip side.

The 51AL on the ring side also used the 554-C subset.

Here is the circuit diagram of this 51-AL / 554-C combination.

References
  • AT&T Specification 4566 (1926) p.64
« Last Edit: February 16, 2015, 05:08:25 PM by unbeldi »

Offline rp2813

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Re: Western Electric 51C desk stand with 554C subset
« Reply #3 on: October 11, 2015, 06:12:22 PM »
I have a 554C that I tried to use with a D1 set -- before I knew better after joining this site.   I could dial out and it rang fine,  but I had a terrible time with the squawky reception quality (the 557 receiver element didn't help matters any) so I replaced the 554C with a 634 years ago, which provided a dramatic improvement.   

Is there any particular wiring scheme or modification for the 554C/D1 arrangement that would improve things, or is a (presumably) anti-sidetone D1 simply incompatible with a 554C?  I'd like to free up my 634 for another application.
Ralph

Offline Jack Ryan

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Re: Western Electric 51C desk stand with 554C subset
« Reply #4 on: October 11, 2015, 06:39:29 PM »
Unbeldi,

Thanks for this summary of the 51C and especially for the use of circuits in your description and for citing the relevant practices. That attention to detail makes it much easier for me to follow up.

I do realise it was posted some time ago but I only saw it when rp2813 commented.

Regards
Jack

unbeldi

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Re: Western Electric 51C desk stand with 554C subset
« Reply #5 on: October 11, 2015, 07:28:57 PM »
I have a 554C that I tried to use with a D1 set -- before I knew better after joining this site.   I could dial out and it rang fine,  but I had a terrible time with the squawky reception quality (the 557 receiver element didn't help matters any) so I replaced the 554C with a 634 years ago, which provided a dramatic improvement.   

Is there any particular wiring scheme or modification for the 554C/D1 arrangement that would improve things, or is a (presumably) anti-sidetone D1 simply incompatible with a 554C?  I'd like to free up my 634 for another application.
The 554C has a sidetone circuit, just like a 534A, except it has an additional condenser to make the automatic number identification (party id) possible.   The 634 subscriber sets are anti-sidetone devices, and indeed should improve audio quality considerably, but how much is subject to the exact electrical conditions of your loop circuit.  I don't know whether your D1 was wired for sidetone (three conductor mounting cord) or for anti-sidetone (four conductor cord) service, so I can't comment on the proper way to connect the set, and I don't want to continue that discussion in this reference board.  If interested let's start a separate post in the General section.  However, as a short note, a 554C can easily be used in place of a 534A subscriber set and it should not impose any audio quality issues in addition to the sidetone limitation.

PS:  This topic discussion is continued HERE.
« Last Edit: October 12, 2015, 09:51:47 AM by unbeldi »

unbeldi

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Re: Western Electric 51C desk stand with 554C subset
« Reply #6 on: October 11, 2015, 07:36:26 PM »
Unbeldi,

Thanks for this summary of the 51C and especially for the use of circuits in your description and for citing the relevant practices. That attention to detail makes it much easier for me to follow up.

I do realise it was posted some time ago but I only saw it when rp2813 commented.

Regards
Jack
Thanks, Jack.   The only way to illustrate these differences in the equipment for message rate service is to use proper circuit diagrams, rather than those ugly WECo wiring diagrams that are almost incomprehensible in their principle functioning.  They were made for servicing (wiring) the equipment, not for understanding and explaining.

Offline Jack Ryan

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Re: Western Electric 51C desk stand with 554C subset
« Reply #7 on: October 11, 2015, 08:18:17 PM »
The only way to illustrate these differences in the equipment for message rate service is to use proper circuit diagrams, rather than those ugly WECo wiring diagrams that are almost incomprehensible in their principle functioning.  They were made for servicing (wiring) the equipment, not for understanding and explaining.

I agree entirely. Thanks again.

Jack