Combined wall handset telephone used by the BPO in CB and Auto areas.

This telephone has a magneto bell and provision in the Bakelite case moulding for three additional keys/press buttons.

Used on extension plans that require an additional gravity springset and more than one press button.

Circuit diagram - N429.

Diagram for Button labels - N620.

History, Technical and General Information on 300 type telephones

Development of the Bakelite Wall Telephone

Collectors information

Keys for use in 300 type Wall and Table Telephones

How to restore Bakelite

Comparison chart of GPO 300 type telephones


Internal view showing a Key No. 303A installed



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Last revised: November 20, 2021