Author Topic: Western Electric 653-BC subscriber set  (Read 1793 times)

unbeldi

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Western Electric 653-BC subscriber set
« on: July 25, 2014, 10:26:43 PM »
The Western Electric 653-type subscriber set is a wall-mounted anti-sidetone telephone with integrated transmitter, dial, ringer and gongs, and network components. It uses a hand-held receiver and switchhook of the same style as a candlestick.

The 653 subscriber set was first introduced in 1931 with the deployment of the anti-sidetone telephone circuit.

The designation -BC indicates a variant of the 653 that was designed for tip-party ID message rate service on two-party lines. The second telephone on the party line for the ring-party station would have been a 653-A, if it were of the same style.

The details of implementation of this telephone type varied as new component became available. Initially it used a 146-type induction coil, while later it used the 101A closed-core device.

The ringer in the 653-BC set has a DC resistance of 1000 Ω (ohm), and it has to have this resistance because the resistance of the ringer is used to indicate to the central office that the set is connected to the tip-side of the line, which identifies the callers telephone number for billing.  When the user lifts the receiver, the ringer is switched so that the tip lead is grounded via the ringer.  Later implementations of tip-party message rate service used a high-impedance ringer that had its coils divided into two sections, one of them having the same 1000 Ω resistance that could be switched as tip-party id.
 
Shown here are three diagrams. The first two represent the late 1930s version of the set, when they were equipped with a 101A induction coil and a 5H dial:
  • A circuit diagram drawn against an equipment label P245021 of 1939 and verified against the BSP.  The equipment label was provided by user gands-antiques.
  • A wiring diagram from BSP Section C63.244 Issue 2 dated 4-18-40. The raw scan was contributed by user Poplar1 from his library.
  • A wiring diagram from the first BSP issue of the 653 sets.  C42.601 Issue 1 June 1 1931, i.e. when anti-side circuitry was introduced. This diagram has been enhanced in color to compensate for the poor quality of the scan. In 1931, the set would have been equipped with a 146C induction coil and 4H dial.

Pictures of a 653-BC are available here:  http://www.classicrotaryphones.com/forum/index.php?topic=12334.msg130097#msg130097


Modification for modern use
The 653-BC can be modified to work on modern lines with bridged ringing:
  • Move the black ringer wire from GND to L1.
  • Move the red ringer wire from YY to RR.
This modification puts the ringer and the 1 MF (1 F) condenser in series and straight across the telephone line on L1 and L2 whether the set is on-hook or off-hook.
The impedance of the ringer is fairly low (1000 ohm at DC), and represents a REN load of about 2 to 2.5.
« Last Edit: March 25, 2016, 11:24:20 AM by unbeldi »