|PRIVATE AUTOMATIC BRANCH EXCHANGES
The 20+100 PABX is a single-unit equipment, having capacity for 20 automatic or C.B. exchange lines (including tie lines to private exchanges if required), 100 extension lines in two separate groups of 50, and 10 connecting circuits.
When the unit accommodates more than 50 extensions, the line-finders for each group of extension lines are connected via group switching relays to their respective connectors, exchange-line and assistance circuits. These switching relays and the second group finders are not provided when 50 or fewer extensions are to be catered for; therefore the cost of the 20+100 PABX when equipped to 50 lines is kept to the minimum.
The exchange lines may comprise a single group of up to 20; alternatively, circuits 1 to 10. may be used for 2 groups of tie lines or constitute a separate exchange line group.
A modern desk-type cordless switchboard is supplied for dealing with incoming exchange calls and assistance calls.
Numbering and Facilities Numbering
Front view of the 20+100 PABX unit, with dust-proofing removed from the lower sections and rear view of the unit, showing dust-proofing in position enclosing the distribution, exchange-line finders and common equipment. The dustproof panels are removed from the lower sections, exposing exchange-line relaysets and extension line relay and finder shelves.
0ptional Service Features
The exterior finish is opaline green enamel; the interior ironwork, apparatus covers and p.v.c. insulated cables are cream. The equipment has a tropical finish. Connecting wires are p.v.c. insulated.
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). (BPO 2000 type 2-motion selectors can be supplied if ordered specially.)
A cross-connecting field is included in the unit, and the line and exchange sides of circuits can be isolated for testing. 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. The switching equipment provided for PABXs of up to 50 lines and over 50 lines respectively is as follows:
The following common items are supplied for each exchange: (a) assistance and night-extension circuit; (b) ringing, tones, alarms, and pulse circuit; (c) marker circuit; (d) unit common services.
The N24119A1T cordless switchboard with 'extension busy' lamps is shown right. The design of the small two-tone grey switchboard accords with contemporary taste and facilitate maintenance. The metal front panel and internal rear equipment frame are both hinged on the metal base so that they can be opened, book fashion, when the ABS copolymer plastic drop-on cover is removed.
Keys have wedge handles with tips of contrasting colour, to enable operated keys to be easily discerned. A hundred lamps, arranged in four 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 for key-sending, intrusion, etc. Supervisory lamps are at the left of the dial, and alarm keys and lamps at top right.
Lamps can be removed without using an extractor. The dial has standard numbering, a 2:1 break/make pulse ratio and a plastic finger plate. A grey plug-in handset, with rocking armature receiver and grey braided extensible cord is provided. A smaller alternative attendant's switchboard is available, with similar facilities, but excluding the extension busy' lamps.
When ordering, please quote PABX 20+100 N24398A1 T
Last revised: October 07, 2019
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