Jack Unit No. 1A and 1B

Jack Unit No 1A and 1B are generally used in conjunction with a Telephone No. 713 and a Mounting Dial Automatic No. 21.  A handset or headset can be plugged into the socket.

The unit comprises of a telephone circuit similar to that of any 700 type telephone, except that it obviously does not have switch hooks, handset or a dial.

The Jack Unit No. 1B is similar to the 1A except it has a printed circuit board and a Regulator No. 6B fitted.

Generally, these were used on Key and Lamp units, exchange supervisors desk etc.

Jack Unit No. 1B
Internal view

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Last revised: March 02, 2021