TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
C3031
Issue 2, Sept 1973 HOUSE EXCHANGE SYSTEM No. 4
Facilities 1 GENERAL
This Instruction describes the facilities provided in a House Exchange System No. 4 (HES No. 4) which has been given the sales name Keymaster 2 + 10. This system provides inter-communication between stations with direct access from these stations to exchange lines. 
2 DEFINITIONS
Multiple Station
A multiple station is one equipped with a Telephone, Intercom No. 4/.... which is an instrument based on the 700 type telephone design. Multiple stations are linked by a multiple cable and are normally confined to one building but the cable may be extended to stations in nearby buildings, if signalling limits are not exceeded. Non-Multiple Extension
This is an extension station connected to the multiple by a two-wire line and a relay-unit. The extension is equipped with a Telephone No. 710 (F or CB). Main Station
This is the multiple station where incoming calls always give an audible signal and which assists non-multiple extensions with calls to other stations. A small key unit is required to be sited with the Telephone Intercom No. 4/1 at this station when non-multiple extensions are provided. The main station also controls some of the additional facilities which may be added to the system. One other multiple station may be designated 2nd choice main station if required. 3 CAPACITY OF INSTALLATION
A HES No. 4 comprises two exchange lines and up to ten stations; exceptionally, one additional multiple station can be provided. A total of four non-multiple extensions or private circuits may be fitted in lieu of four multiple stations. The system also includes a Power-Unit No. 52A and an exchange line relay-unit, together with a relay-unit for each non-multiple extension or private circuit that has been provided; these units are all wall mounted. |