GEC
MXE 72

Semi-automatic Small Private Branch Exchange

MXE 72 is the PBX for small organisations where personal service and low cost are of first importance.  It sets a new standard in small-PBX design by combining the simplicity of person-to-person connection via fast operation keys on an operator's switchboard with the benefits of many features only found on fully automatic systems.

Up to 10 public exchange lines and 72 extensions can be provided, but the modular equipment practice ensures that this PBX can be tailored to suit any individual requirements.

The MXE 72 package incorporates an attractive desk top switchboard with a separate cabinet for the switching equipment.  The power supply and main terminating frame are built into the cabinet.

The switchboard features direct extension selection and pushbutton working with all types of public exchange.  A logical operating sequence allows calls to be processed quickly and efficiently, and its simplicity enables the untrained user to become proficient with minimum instruction.

Installation is simple.  To ease handling the MXE 72 is delivered as a set of units which are rapidly assembled on site, so there are no problems in installing the equipment in difficult locations.  The switching cabinet itself is compact, virtually silent in operation, and entirely suitable for the office environment although it may be installed remote from the switchboard in any out-of-the-way place if preferred.

Expert staff are not needed to maintain the MXE 72. The crossbar switching matrix, long-life relays and solid-state components are inherently reliable, but if a malfunction does occur, swing-out gates make inspection and servicing easy.  When alterations or additions are required to the line plant, a door on the right of the cabinet allows unrestricted access to the main terminating frame area.

STANDARD FEATURES
Operator's switchboard with:
Direct extension selection
Pushbutton dialling with all types of public exchange
Key-per-trunk operation
Adjustable tone ringer
Momentary operation keys
All exchange lines busy' indication
Call split
Extension-to-extension calls via Operator.
Incoming calls via Operator. Outgoing calls via Operator, either Operator or extension dialled.
Operator's busy override (with warn tone) and camp-on.
Operator recalls and transfer of public exchange calls.
Distinctive ringing for public exchange and internal calls.
Automatic release on all calls.
Automatic hold on public exchange calls (selected by system strapping).
Operator's overflow link.
Waiting call 'meet me'.
Non-blocking switching matrix.
Fixed or flexible night service (selected by system strapping).
Mains fail switching.
Switchboard testing at equipment cabinet.

OPTIONAL FEATURES
Direct outward dialling (DOD) for any number of extensions.
Metering on public exchange calls.
Tie Lines.
Long-line extensions.
Operator load control of public-exchange access for DOD extensions.
Ring tone to calling extensions and Operator on internal calls.
Operator's switchboard in teak with light green top panel.

Technical Summary

Switching Equipment
Mounted on 2 or 3 swing-out gates according to size of system required and housed in a single metal cabinet.
UP to 10 + 36 lines (including options) - Gates 1 and 2.
Up to 10 + 72 lines (including options) - Gates 1, 2 and 3.

Switchblock
Single stage, non-blocking full availability crossbar array.

Operator's switchboard
Available in all-white, or teak with green top panel.
Systems above 36 extensions catered for by a matching adjacent unit or larger switchboard, to customer requirements.
Keypad output: 10 i.p.s. or DTMF to CCITT recommended frequencies.

Extensions
Up to 72.  Non-DOD extensions available in groups of 18, DOD extensions in groups of 9.

Public Exchange Lines
UP to 10.

Local Links
Two or four, plus operator's overflow link.

Extension Line Loop Limits
500 ohms standard, 1300 ohms optional for long fine extensions, including telephone instrument.

Ringing
25 Hz, 0.7 sec on 1.35 sec off (internal calls).
25 Hz, 1 sec on 3 sec off (public-exchange calls).

Ring Tone (optional)
360/450 Hz, 1 sec on 3 sec off.

Warn Tone
Pulses at 2 Hz.

Crosstalk Coupling
Better than -75 dB.

Insertion Loss
Less than 1.5 dB, 500-3400 Hz. (Public exchange lines)

Cabinet Weight
10 + 36 lines: 303 kg (680 lb) max.
10 + 72 lines: 370 kg (830 lb) max.

Primary Power Requirements
110/200-240v 50-60 Hz 320vA max.

Dimensions
Height: 52in (1320mm)
Width: 50in (1250mm)
Depth: 23in (600mm)

Equipment - cabinet dimensions are the same for 36 and 72 line exchanges

A 36-line switchboard console can be expanded to 72 lines by the addition of a extension unit.

1975

GEC Telecommunications Limited