These are selectors that were originally used in UAX13 equipment

These UAX13 selectors were chosen as they have the ability to use a vertical marking bank to deny access to any chosen level.
It was found necessary though to change the usual 3000 type 11 ohm HX battery testing relay for something more sensitive as PABX4 finals have a 250 ohm testing battery compared with the usual 150 ohm battery in a UAX13 final. A high speed relay was found to be suitable. Both single and twin type contacts have been used. Two diagrams have resulted from the modification of two distinct UAX13 first selectors.

The TM relay is not required in this role and has been removed.

Show Issue C Circuit Diagram as a PDF

Show Issue D Circuit Diagram as a PDF

Page provided by John Bathgate This page was last updated on 27th August 2016