Australian Post Office
Telephone No. 27
Common Battery, Wall, Main and Extn Switch (W.E.)

Telephone, Common Battery, Wall, Main Set with Extension Switch (W.E. Type)

The main and extension phones of a Western Electric CB one-line intercom.  This illustration of the switching unit is probably correct, as its circuit matches that in the 1914 Technicians' handbook fairly closely.

The main phone used a 3-position switch on the switchbox to connect to the extension and had separate bells to signal calls from the extension and calls from the exchange.  The extension bells are located just under the writing slope on this example.

The extension phone, the Telephone No. 29, used a generator to signal the main phone, and could be any suitable magneto telephone.

Taken from Bob's Old Phones

Diagrams

 

Last revised May 31, 2025

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