**PRIVATE AUTOMATIC BRANCH EXCHANGES**

'MULTIPHONE' SYSTEM

A 24-volt low-cost system of up to 4 + 10 lines without a manual switchboard.

P.A.B.X. 5+20

A 50-volt fully automatic subscriber-attended, non-extensible single-unit equipment
employing linefinder and connector uniselectors. Capacity: 5 exchange lines, 20 extension
lines and 4 connecting circuits. A simple cordless switchboard can be supplied if
required.

P.A.B.X. 10+50

A 50-volt non-extensible single-unit equipment employing linefinder uniselectors and
2-motion connector switches. Capacity: 10 exchange lines, 50 extension lines and 7
connecting circuits. Includes a desk cordless switchboard.

P.A.B.X. 20+100

As P.A.B.X. 10+50 but capacity for 20 exchange lines, 100 extension lines and 10
connecting circuits.

P.A.B.X. 3 (B.P.O. No. 3)

A 50-volt extensible equipment for any requirement above 50 extension lines. Employs
linefinder uniselectors, 2-motion group and final selectors, and a floor pattern cord-type
switchboard.

P.A.B.X. E.T.4

A 50-volt extensible equipment similar to P.A.B.X. 3 but employing floor pattern
console-type cordless switchboards and offering more facilities.

**The PABX's below are not included as they are used as Rural
Exchanges**

**'RURAX' TYPE P.A.B.X. 8**

All 50-volt systems extensible to a normal capacity of 350 lines and employing uniselector
type switches as linefinders, connectors and, when necessary, group selectors.

**P.A.B.X. ERP.1A**

For small installations requiring only basic facilities and not more
than 10 exchange lines. Includes a table type cordless switchboard. 10+50 lines and 8
connecting circuits accommodated on one unit.

**P.A.B.X. ERP.3**

For larger installations requiring more facilities. Any number of
exchange lines can be provided. Includes a floor pattern cord switchboard. Up to 12
connecting circuits per 50-line group.

**P.A.B.X. ERP.4
**A flexible system with comprehensive facilities and many special
features. Employs one or more desk type key-sending cordless switchboards. Up to 10
connecting circuits per 50-line group.

**Mining P.A.B.X's IN THE UNITED KINGDOM**

The British Post Office exercises control over P.A.B.X's in the U.K. There are two types as follows

**P.A.B.X. B.P.O. No. 2.
**Capacity 10 exchange lines and 49 extension lines. This
is rented from and installed and maintained by the B.P.O. who also supply all telephones
of non-certified type, the associated line plant and the P.A.B.X. power plant. Safe
telephones, coupling and switching units are purchased by the customer from the
manufacturer. The B.P.O. install and maintain all surface equipment including the coupling
units and safe power equipment. The customer installs and maintains the shaft cable and
the underground telephones. Enquiries for P.A.B.X.2 should be addressed to the B.P.O.
telephone manager's office in the area concerned.

**P.A.B.X. B.P.O. No. 3.
**Unlimited exchange/extension line capacity. Purchased,
together with all the required certified safe equipment, from the manufacturer. The B.P.O.
supply and install the non-safe surface telephones, line plant and P.A.B.X. power plant on
rental, and maintain these together with the P.A.B.X. and safe coupling equipment after
installation by the manufacturer. The customer installs and maintains the shaft cable and
underground telephones. The B.P.O. telephone manager for the area should be informed by
customers who have contracted with the manufacturer to purchase P.A.B.X.3 equipment.

Taken from the Ericsson Catalogue No. 60

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