TRANSFORMER No's 431A and 431B
This was a module type transformer that was used when a Handset No. 7 (Neon) was fitted on a 700 type telephone.  It had a one metre fly lead connected to the output.

The transformer was rated to have an input of 200-250vac and an output of 75vac at 0.5A.

It came in two models, the No. 431A and 431B, the A variant was fitted with round pins to BS 546 and the B variant was fitted with oblong pins to BS 1365.

The unit contained two Fuses No. 48/0.5.

Introduced in 1964.

Dimensions
2.6" high x 2.2" wide x 2.3" wide.

In 1975 the Transformer was re-designed and the round pin connections were dropped and only connections to BS1365 were available.  The module contained a Fuse No. 73/0.8 and a Fuse 48/0.5.

Drawing - CD1981.

Specification - D2282.

Transformer No. 431A

 

Transformer No. 431B

 

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

Last revised: September 02, 2024

FM