|PRIVATE AUTOMATIC BRANCH EXCHANGES
10 + 50 PABX
This is a single-unit equipment having capacity for 10 exchange lines, 50 extension lines and 7 connecting circuits. A desk-type cordless switchboard is supplied for dealing with incoming exchange calls, and assistance calls. The stock unit, equipped for 4 exchange lines, 30 extension lines and 4 connecting circuits, is fully wired to facilitate extension. Up to 5 tie lines to other private installations can be provided. The total of exchange and tie lines must not exceed 10. Both are normally arranged for auto or C.B. working. Maximum extension-line loop resistance including the telephone is 800 ohms. Exchange and tie-line loop resistance may be up to 1,000 ohms depending upon the limits imposed by the remote exchange equipment.
Numbering and Facilities
Numbering Extensions are numbered 20 to 69. Single-digit dialling codes 7, 8, 9 and 0 are used for (a) exchange lines (b) tie lines or a second group of exchange lines (c) assistance (d) night service answering.
Optional Service Features
Message waiting; message registration; conference; trunk barring; extension busy' lamps; direct access key calling and staff location.
Components are of standard BPO type and proven reliability. They include N30000 (BPO 3000) and N45000 (BPO 600) relays, heavy- duty line-finder uniselectors (BPO No. 2) and 100-outlet 2-motion selectors N46600 (BPO 4000). If specially ordered, selectors N43200 (BPO 2000) can be supplied. Excepting strip-mounted line and miscellaneous relays, all circuits are on jack-in mountings to facilitate extension.
On one side of the unit are line relays, exchange and tie-line relay sets and fuse panels; on the other, the finder uniselectors, 2-motion selectors and connection strips. Connection strips ('line' and 'exchange') are mounted under a cover at the side of the unit and serve for the distribution of incoming lines, cross-connection being made by means of screw terminated jumpers. Line protectors are provided complete with heat coils and fuses on a separate wall mounting for 10 circuits when ordered.
The 25Hz and 400Hz ringing and tone frequencies are generated by transistor-type oscillators powered from the 50v exchange supply. These static devices require little maintenance and do not cause interference with radio signals.
Keys have wedge handles with tips of contrasting colour to enable operated keys to be easily discerned. Fifty lamps, arranged in two rows, are 'extension busy' lamps, fitted only when specified. The upper row of double-throw keys and associated lamps are for exchange-line, tie-line, manual extension, assistance and miscellaneous circuits. The lower row of keys, again of double-throw type, serve as key-sender digit keys when operated downwards, and provide for exchange and extension release, flash, test, speak, etc., facilities when operated upwards.
Lamps can be removed without using an extractor. The dial has standard numbering, 2:1 break/make pulse ratio, and a plastic fingerplate. A grey plug-in handset with capsule receiver and grey braided extensible cord is provided, and 6Oft(18.29m) of p.v.c. insulated cable to connect the switchboard to the PABX unit.
Last revised: October 07, 2019