This page explains how to mount a BPO 100 or 200 Pyramid style telephone onto a Bakelite Bellset.  To start with the Bellset must have the special two threaded screws.  These came as standard on early Bellsets, but were replaced by ordinary single threaded screws later on. 

The correct screws are shown to the right and have slotted heads with a thread down the centre. The inner top and outer bottom threads are 2BA, whilst the centre threaded section is 0BA..

The special screws should be removed from the Bellset cover and then offered directly into the screw fixing holes of the Bellset chassis, from the rear.  The screws should be screwed past the two threaded sections until they are right against the Bellset and are free to turn.  The picture below shows a rear view of the Bellset with the two screws in place.

Generally the Bellset was fixed to the wall, so there were not a lot of phones with Bellsets attached to phones in circulation.

The two fixing screws fully in place
 This view shows the two fixing screws from the front of the Bellset
 Assembly procedure
  1. Offer the Bellset cover (1) onto the Bellset (2) itself.
  2. Place the Telephone body (3) onto the combined Bellset and cover (1 & 2).
  3. Screw the special screws into the Telephone body, until the Bellset is firmly fixed to the phone.
  4. On the Telephone base, open the drawer fully.
  5. Screw the Telephone base (4) onto the bottom of the Bellset.
  6. Shut the drawer, it stops against the Bellset cover.


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Last revised: January 10, 2016