This selector was designed and built around a mechanism and relays that were to hand. It is just a bit of fun really but does seem to do the job very well.

It's rather interesting to have this foreigner taking its place in the UAX13.

This circuit diagram has been based closely on the usual 2000 type first selector diagram but the following changes have been made :

The release circuit has been modified so that the release condition is directed to the release magnet by contact B2 rather than the rotary magnet.

The CD hold condition is normally via a low resistance winding through which the vertical magnet current flows. Such a relay was not available so the hold winding here is 1000 ohms and is energised by a second set of contacts on the A relay.

The HX relay is normally an eleven ohm 3000 type, but this was not available so a low resistance high speed relay has been substituted.

The TM relay in a normal first selector has been omitted completely as it would have no function in an incoming selector.

The vertical marking bank and relay CC have been retained as this permits levels (eg ring back on level 9) to be barred to incoming traffic.

The incoming P wire has been retained as the earth returned on this wire when the selector is in use is used to operate the call count meter on the incoming circuit.

A selector in use lamp has been provided.

Show 4000 Type Incoming Junction Selector Circuit as a PDF

Page provided by John Bathgate This page was last updated on 6th November 2014