final selector

Calls were switched over two, three or four group selection stages followed by a final selector.

The incoming final selector performed a sleeve test to detect a busy line.

The last two digits dialed would operate the connector switch (final selector in Britain).

A Panel Final Selector frame is on display at the Museum of Communications.

The subscriber can now dial the final two digits, the final selector steps up, then round according to those digits.

The same process occurs - the second G/S steps up, then hunts round until it finds a Final Selector.

This allowed a PBX group to have up to 20 lines without the need of 11-and-over PBX final selectors.

For local calls, a piece of equipment called a Local Call Timer (LCT) was in circuit between the final selector and previous group selectors.

The original final selector (connector) switch which connected to 100 customers was supplemented by preceding group selector stages, as the "cascading" enabled connection to many more customers, and to customers at other exchanges.

The translated digits were sent to the code selectors, and then the four numeric digits were sent to three switching stages in the terminating exchange (two group selectors and a final selector).

In practice to save space 200-outlet final selectors were almost always used in preference to 100-outlet; the selectors switched to the alternate wipers, or not as appropriate, depending on which preceding selector stage seized them.

Moreover, if these selectors were used, the PBX group could have up to 200 lines, and the final selectors in the group were arranged so that different selectors searched over the lines in a different order to reduce waiting times for callers.