TELEPHONE No. 28


A Local Battery handset with battery cut off switch fitted in the handle. Being local battery it requires a battery power source at the telephone.

The handle is made of Ebonite with an integral switch.  The switch connects the telephones local battery into circuit which then powers the transmitter.

Originally called the "Telephone, Micro" by the GPO.

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

Fitted with a 4 way cord.

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

Telephone No. 28A was used at Brighton and Glasgow only, and had no 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:-
1 x Suspender, Microtelephone No.2.
1 x Hook, Receiver E or No. 12.

No. 28, with Loop and Cord 4/15A, Brown, 48" (1928 and 1946)
Used with:-
1 x Loop, Telephone Suspension, No. 1 added
1 x Cord, Instrument No. 4/15A, Brown, 48" substituted for Cord, Instrument 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 - - -

Note: The Transmitter No. 10 includes a Mouthpiece No. 1 and a Transmitter-Inset No. 3.

Circuit diagram - N128.

Drawing - 8241 (Mark 4).

 

 

 
BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: December 30, 2024

FM