TELEPHONE No. 28


Local Battery handset with microphone cut off switch fitted in the handle.  The switch connects the telephones local battery which powers the microphone.

Originally called the "Telephone, Micro".

This handset was used on many early telephones and could be fitted with a loop or hook suspension.

See also:-
Telephone Efficiency Committees Report on Local Battery Area telephones.

Telephone No. 28A was used at Brighton and Glasgow only, and had no cut off switch.

Telephone included (1946):-
Telephone No. 28, with press switch.
1 x Connection, Mouthpiece No. 1.
1 x Diaphragm No. 12.
1 x Cord, Instrument No. 4/17A, Brown, 48" (earlier Mouthpiece No. 1 supplies fitted were with No. 4/03A, Brown, 48").
1 x Earpiece No. 14.
1 x Receiver 150 ohm.
1 x Transmitter, Inset No.3.

No. 28, with Loop Loop, Telephone Suspension, No. 1 or No. 2 added. (No. 2 added for Mark 237 only) (1928 and 1946).
Used with:-
Suspender, Microtelephone No.2.
Hook, Receiver E or No. 12.

No. 28, with Loop and Cord 4/15A, Brown, 48" (1928 and 1946)
Used with:-
Loop, Telephone Suspension, No. 1 added and Cord, Instrument No. 4/15A, Brown, 48" substituted for No. 4/03A, Brown.
To be requisitioned separately - Plug No. 401.

No. 28A, without press switch - for Brighton and Glasgow only (1928).
1 x Connection, Mouthpiece No. 3 or 4.
1 x Diaphragm No. 23.
1 x Cord, Instrument No. 421 modified.
1 x Earpiece No. 12.

No. 28, with press switch (1928)
Refer to table below:-

Item Mark Number
234 235 236 237 NT2 NT3 NT
Connection, Mouthpiece No. 1 1 1 1 1 1 1 1
Cord, Instrument No. 403 - 1 1 - 1 1 1
Cord, Instrument No. 417 1 - - 1 - - -
Diaphragm No. 12 1 1 1 1 - - -
Diaphragm No. 18 - - - - 1 1 -
Earpiece No. 2 1 1 1 1 - - -
Earpiece No. 8 or 9 - - - - 1 1 -
Earpiece No. 13 - - - - - - 1
Earpiece No. 14 - - - 1 - - -
Mouthpiece, No. 1 1 1 1 1 1 1 1
Receiver (ohms) 150 150 150 150 120 120 150
Ring, Receiver Adjusting NT 1 - - - - 1 1 -
Transmitter No. 10 - 1 1 - 1 1 -
Transmitter, Inset, No. 3 1 - - 1 - - -

Circuit diagram - N128.

Drawing - 8241 (Mark 4).

 

 

 
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Last revised: July 03, 2024

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