Working on Strowger principles, the type 109 Private Automatic Exchange (PAX) is designed for large organizations whose requirements range from 100 extension lines upwards.
One of the characteristics of this PAX is its capability of being extended to an unlimited number of lines by the addition of racks equipped with 50 or 100 extension lines. The number of simultaneous calls depends on the amount of switching equipment installed.
The components i.e. selectors, uniselectors, relays, etc. are identical to those used in Strowger type public exchanges manufactured by P.A.E.P.
This PAX works with desk or wall type automatic telephones, a description of which is given in the corresponding catalogue.
The extension line equipment, linefinders and selector hunters are mounted on the combined racks in two distinct groups. Each group consists of 50 line circuits, 10 linefinders, 10 selector hunters and associated control circuits and 9 or 10 final selectors.
The ringing current and tones relay set is also located on this rack.
The group selectors are mounted on racks having a capacity for 60 selectors on 6 shelves of 10 each.
A ringing current and tones relay set is supplied for each 200 extension lines.
The equipment is mounted on grey finish racks 2.286m (7’6”) high, 1.371m (4’6”) wide and 0.393m (1’3”) deep.
The majority of the equipment is of the “jack-in” type. This method of mounting permits the easy removal of the equipment for maintenance purposes and the extension of equipment without additional wiring.
Two-motion 100 outlet group and final selectors of the BPO type 2000 are used.
The uniselectors are of the heavy duty BPO No. 2 type: BPO type 600 relays are used in the extension line circuits, BPO type 3.000, thermal and high speed relays are used in the other circuits.
All selectors and relay sets are fitted with covers as a protection against dust.
The power equipment normally comprises a 50V battery paralleled across the output of an appropriate automatic float battery charger.
The battery should have sufficient capacity to operate the PAX for 8 to 10 consecutive hours in the event of a mains supply or charger failure occurring.
A high/low volt alarm circuit can be supplied which operates when the maximum or minimum voltages are exceeded.
A main distribution frame of adequate capacity is supplied fitted with appropriate term mating equipment, depending on the customer’s requirements.
CONVERSION FROM PAX TO PABX
This PAX, even after it has been in service, can easily be converted into a PABX (type 211) by simply installing the additional equipment required (exchange line relay sets, attendants position etc.).
Taken from sales literature 211/1 by Plessey Automatica Electrica
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