TELEPHONE No. 121 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Wooden cased wall telephone used on CB and Automatic systems. Made from around 1924 and can be found in the 1928 GPO Rate Book. There were two variants, the Mark 234 and the later Mark 2. Click here for an explanation of the "Mark" system. All models are fitted with a Receiver, Bell No. 1A, but the Mark 234 was fitted with a Transmitter No. 1 and a Coil, Induction No. 14, whilst the Mark 2 was fitted with a Transmitter No. 22 and a Coil, Induction No. 18A. Terminal numbering/lettering and the wire colours also differed - see tables below. Terminal Equivalents
Dial terminal Strip
The dial mount is a Mounting, Dial, Automatic No. 7. The housing is called a Case No. 1 and could be constructed of American Walnut, Black Chuglam, Pyinma, Halou, Tasmanian Myrtle or African Mahogany. The casing front door is secured, on the left side, with a sprung loaded, retained, screw. Many of these telephones were converted from Bellset No.1's. On the rear of the phone one may well find the original Bellset No.1 crossed out and TELE 121 stamped nearby. Some were converted by the BPO factories into the Telephone No. 251, which are identifiable as they have a handset instead of the bell receiver and front mounted transmitter. This telephone is similar to the Telephone No. 101 but with a dial fitted below the transmitter. Because this telephone is sought after by collectors, they have become rather difficult to find. A number of reproduction instruments have appeared in the market place, generally made up from Bellsets No. 1 or from railway omnibus circuit telephones. Many of these telephones were later converted by the GPO into the Telephone No. 221. The early type used a Transmitter No. 1 which could have Label No. 43 fitted between the speaking tube and the transmitter body. This label advised of the Exchange name and number. This telephone superseded the Telephone No. 105. Mark 234 Telephone includes (1928 Rate Book):- Desk No. 4 to be requisitioned separately when required. Mark 2 Telephone includes (1946 and 1956 Rate Books):- To be requisitioned separately when required:- Variations Telephone No. 121L or F was fitted with and Dial, Automatic No. 10FA or 10LA (supersedes Telephone No. 105). Telephone No. 121 Mark 2 was fitted with the "improved" Coil, Induction No. 18 and Transmitter No. 22. Telephone No. 121B was supplied with a Dial, Automatic No. 10BA for use in the Brighton Area. Telephone No. 121L was in general use on Automatic exchanges in large exchange areas and fitted with a Dial, Automatic No. 10LA and a Label No. 43C. Telephone No. 121S was supplied with a Dial, Automatic No. 10FS and used on Siemens systems in Grimsby, Hurley, Ramsey, Southampton and Stockport areas (superseded the Telephone No. 77). Telephone No. 121W was supplied with a Dial, Automatic No. 10FW and used on S.T. & C's exchanges at Darlington and Dudley (superseded the Telephone No. 65). Manufactured by: Variants: The Australian Post Office also used the same telephone - their Telephone No. 137AW which was identical to the Telephone No. 121 Mark 234. Circuit diagram - N221. Circuit diagram - AT 1728. Drawing Numbers - 8642 & 60490 (Mark 2). The Mark 2 diagram is dated 1934. Collectors Information - what to look for How to convert a Telephone No. 121 to Plug and Socket Telephone mouthpiece sanitisers See also the Telephone Efficiency Committees Report on Common Battery Area telephones. Additional Pictures
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Last revised: May 13, 2024FM |
Early CB versions had a notice frame
fitted under the transmitter (shown pictured to the left, and called the Frame, Notice No.
1) whereas later CB telephones had a dummy dial cover instead of
the frame. Many of these telephones are seen on a backboard with a writing shelf
called a 
