Wall mounted Bellset for internal use, generally found in customers premises.  They were always hard wired into the telephone line.  Only the Bellset No. 50E came with a line cord.

Fixed to the wall with a 'T' shaped metal bracket, the same bracket used on 700 type wall phones.

The cover is plastic and were available in grey and ivory.

To remove the cover on the Bellset No. 50A - 50D:-
Grasp the lower edge of the cover and pull toward yourself.  The cover will easily unclip and once it is swung out about an inch then lift the cover upwards to dislocate the upper clip.  Refitting is the same principle but in reverse.

To remove the bellset from the wall mounting on the Bellset No. 50A - 50D:-
Remove cover as above and then locate the screw fitted centrally at the lowest part of the bellset.  Once the screw is release, then grasp the bellset at the lower edge and pull towards you.  Swing upwards about an inch and pull the top end away from the wall bracket clips.  Refitting is the same principle but in reverse.

Circuit diagram N550.
Drawing 93314.

Bellset No. 50A
Standard Bellset (1000ohm bell ringer & capacitor). Supersedes Bell No. 59A and Bellset No. 26.  Superseded by Bellset No. 50C.
Fitted with Bell No. 59C-1 and Telephone-Unit 1/D93315.

Bellset No. 50B
Bellset containing a Telephone No. 746 circuit for use with Telephone No. 713.  Supersedes Bellset No. 48.  Superseded by Bellset No. 50D.
Fitted with Bell No. 59C-1 and Telephone-Unit 2/D93315.

A Buzzer No. 32C-3 can be fitted to the circuit board mounting brackets.

Bellset No. 50B (did not come originally with a cord)

Bellset No. 50C
Standard Bellset for new plan (PST - 4000 ohm ringer & capacitor).
Fitted with Bell No. 59D-1 and Telephone-Unit 1/D93315.  This Telephone-unit was originally the same size as a telephone circuit board but later on was miniaturised.  Both circuit boards are shown below.
Plastic cover in grey or ivory.

Bellset No. 50C (cover on) Bellset No. 50C (cover removed)
This Bellset shows the small Telephone Unit

Bellset No. 50C using Telephone-unit 1/D93315

Bellset No. 50D
High impedance version of the No. 50A for use with Telephone No. 713.
Fitted with Bell No. 59D-1 and Telephone-Unit 2/D93315.

Bellset No. 50E
High Impedance Bellset with 3 Metre cord for use on PST, supersedes Bell Sets No. 50B & 50C for new supply and maintenance replacement, available on sale or rental terms (shown below).

Bell No. 50E, Denis Ferranti Ltd.

Bell Set No. 50E - S/1000/23/K/501724

Modifications which have not received appropriate approval must not be carried out as to do so would invalidate approval making connection unlawful.  Bell Set No. 50E or 'Extension' line cord may be shortened without breaching approval.

For interior wall mounted use, supplied with plug ended cord for use with any phone socket.

Measures approx. 145mm x 145mm x 57mm, weight 470 grams.

Comes with 2 wood screws, wallplugs and template for positioning screws.

Ringer has a REN 1.

The Line cord of Bell Set No. 50E or 'Extension Tonecaller' may be cleated in place using Cleats Wiring 4C and if necessary be shortened (to a minimum length of 300mm) where bell/tone caller is to be fitted adjacent to phone socket.

Bell Set No. 50B (Low Impedance bell set for use with hard wired, series connected extension bell arrangements) are no longer available centrally on BT.  Local stocks should only be used to maintain existing hard wired installations, when local stocks exhaust, faulty Bell Sets No. 50B should be maintenance replaced by Bell No. 50E and system converted to PST.  Existing serviceable Bells Sets No. 50B and 50C may be used for internal shifts.

Taken from BT information

Connecting a PST line cord to a Bellset No. 50C
Follow the following instructions:-

  1. Connect white wire of line to terminal B7.
  2. Connect red of the line cord to terminal B9.
  3. Connect green of the line cord to terminal E.
  4. Connect blue of the line cord to terminal B3.


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Last revised: November 03, 2020