ERICSSON Type A
P.A.B.X.

This equipment operates on a line finder basis, the functions of which are similar to those described previously for A.E. Co. 30/30 type and G.E.C. "G.P.O." system. The line finders are 50 point uniselectors, an idle one of which is selected by an assigner, upon the origination of a call. When the calling line is found by the line finder the assigner is released and becomes available to other callers.

Equipments up to 80 lines capacity operate on a two digit basis and 100 outlet final selectors only are employed, being directly associated with the line finder.

For equipments of more than 80 lines capacity group selectors are fitted and three-digit working is introduced.

The group selector can, however, be in the form of a uniselector, thus economising in wiring and space.

Two-digit equipments are arranged as regards wiring, so that group selectors can be readily introduced if at any time the capacity of the installation grows beyond So lines.

The apparatus is mounted on G.P.O. type single sided racks 2' 6" wide and 7' 0" high. It consists of two shelves of line finder uniselectors and two shelves of final selectors together with the necessary alarm and assigner equipments.

Each line finder shelf contains five uniselectors which serve a group of 40 lines. The two shelves therefore serve 80 lines.

Other features
All relays are fitted with twin contacts, thus reducing duty contacts to a minimum.

If the assigner fails to find an idle line finder within 9-18 seconds an alarm is brought in.

The system operates on 50 volts.

Taken from a paper by the IPOEE dated 1932 (No. 142)