PRESS BUTTON UNIT No. 4
This an MF press button unit that consists of a 12 button keypad marked 1 to 0, # and *.  The push-buttons are arranged in 3 columns of 4.

The push-buttons are arranged in 3 columns of 4.  The 11th and 12th button tops are marked * and # respectively.  The * and # buttons are required for providing additional facilities in the future, and serve no purpose at present.  Depression of either of these push-buttons will send a combination of tones to line.

The keypad will only work when connected to MF (DTMF) systems.

Variants:-
PBU No. 4A is fitted in Telephones SA4258 and 2/SA4258.
PBU No. 4B is fitted in Telephones 4/SA4258.
PBU No. 4C is fitted in Loudspeaking Telephone SA4265.

 
 
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Last revised: July 24, 2025

FM