GEC PABX 5+20

5 + 20 line
private automatic branch exchange

STANDARD FEATURES
Maximum capacity
5 public-exchange lines; 20 extension lines.

Connect circuits
Provision for4 simultaneous inter-extension calls in addition to a maximum of 5 public-exchange calls.

Numbering scheme
30 to 49 for extensions; 1 or 2 for tie lines.

Public exchange service
Outgoing: direct access from extensions after operating a pushbutton switch on the telephone.  Individual extensions can be prevented from dialling public-exchange calls.
Incoming: No operator's switchboard is required; a call is answered at one of up to 8 designated extensions and routed to the required extension by the enquiry and transfer method.  The call can be offered to an extension already engaged.

Enquiry and transfer
Telephones with a pushbutton can be supplied* to all or selected extensions to enable a public exchange call to be held while the user calls another extension with an enquiry.  When the enquiry is complete, the original extension returns to the public-exchange call, or can transfer it to another extension.

Executive's priority
Selected executives can break into an existing conversation by dialling an extra digit '1'.

Mains fail protection
Public-exchange lines can be connected automatically to designated extensions in the event of an AC supply mains failure.

OPTIONAL FEATURES
Tie lines*
1 or 2 on one route only.

Conference*
Designated extensions can be connected together via a special circuit.

Staff location*
Staff absent from their offices may be called by dialling a special locating number and a personal code, to operate lamps or bells.

Secretary service*
A secretarial switching telephone enables secretaries to filter calls to an executive.

Route restriction*
Individual extensions may be permitted to dial local but not long distance calls.

GENERAL
Mode of operation
Fully automatic operation using uniselectors and relays.  All conversations are secret from each other.

Tones and ringing
Mains-supply derived dial tone, ringing tone, ringing current and executive intrusion tone; electronically derived busy, number-unobtainable and link throw of tones.  When the exchange operates from a battery power supply, all tones and ringing current are provided by an all-electronic tone generator.

Signalling
Required dial-pulse characteristics: 7 to 14 i.p.s., 2:1 break to make ratio.

Alarm
Audible indication of blown fuse.

Power unit*
Built-in AC power unit: input, 100 to 120V or 200 to 250V 50 to 60 Hz single phase.
or
External Battery: 50V 32AH ; with float charger, input as for AC power unit, output 50V d.c 3A.

Line-loop resistance
Not to exceed 1000 ohms.

Construction
Wired-in units on a framework, hinged for easy maintenance, and contained in a steel cabinet (painted dark green) with hinged doors.

Dimensions and weight

*To be specified when ordering