HTS No.1


TELECOMMUNICATIONS INSTRUCTION
C MARKETING - INSTALLATION
3 INTERNAL
M4000

HOUSE TELEPHONE SYSTEM No. 1

General
This Instruction describes the House Telephone System No. 1 of internal communication without exchange line facilities which the P.O. can provide for subscribers at their request. Engineering officers receiving such requests should refer the inquirer to the T.M. (Sales Div). Telephone House No. 104 is shown to the right.

Facilities
The House Telephone System provides direct intercommunication without secrecy between a number of stations all of which must be within the same premises. Access to exchange service lines cannot be given, nor can internal conference calls be established.

Description
Table and wall instruments are available for 5, 10, or 15 station capacity. Each instrument has 5, 10, or 15 buttons, a handset with a non-polarised receiver (similar to a Receiver Inset No. 2P but without a permanent magnet) and a buzzer. A multiple cable connects the instruments together and distributes power for signalling and speaking from two common batteries of dry cells.

Although table and wall instruments are supplied they are identical except that the table set has a cord and terminal block for external connections, while the wall set is usually wired direct. The table set can be converted very simply for wall mounting by undoing two nuts and screws and reversing part of the telephone cradle.  A Telephone House No. 105 is shown to the right.

Diagrams for the system are contained in the Q(L) series and are:-

Q(L) 351 Internal wiring-terminal block connections
Q(L) 352 Typical cabling
Q(L) 353 Schematic of a station to station call

The instruments used are now included in the Rate Book where they have the description Telephones, House, No 101 to 105.

Method of operation
The desired station is called by lifting the handset and pressing the appropriate button to its fullest extent. When pressure is released the button automatically restores to an intermediate speaking position. The buzzer at the distant station operates whilst the button is fully depressed and the person called lifts the handset to reply.

Numbering of stations
Stations should normally be numbered in sequence according to their position in the multiple cable.

Installation
Table 1 gives the cable and telephone associated with each size of installation.

Applications involving abnormal requirements or external wiring should be assessed in accordance with A0030.

TABLE 1
Number of Stations Telephone House No..... Type Wiring Size
5 100 Table 12 wire
5 101 Wall 12 wire
10 102 Table 21 wire
10 103 Wall 21 wire
15 104 Table 21 wire
15 105 Wall 21 wire

NOTE: At installations where the number of stations is likely to increase and exceed nine, a 21 wire cable should be provided initially.

Installation in unsuitable situations
Very damp or dusty situations are unsuitable for House Telephone Systems. If damp situations are found to exist during the installation of a system, the positions for the terminal blocks and the wall telephones must be chosen to avoid them. The cables should preferably enter the terminal blocks from below to prevent moisture which may condense on the cable sheaths from running into the blocks.

Cable limits
The length of cable between the extreme end stations of the system should not exceed 140 yards. If it is necessary to exceed this limit by a short distance an additional cell may be added to each battery.

Fitting the telephone
(a) Table type - The terminal block supplied with these instruments consists of three parts: a metal base with a raised central pillar, a tablet with terminals on both front and rear sides, and a moulded cover. The metal base should be securely fixed to a wall or other mounting.
The instrument cord conductors are laid out and secured to the terminals on the rear side of the tablet. The cable from the Box, Junction, House or Block, Terminal, No. 37A should be neatly arranged and terminated on the terminals at the front side of the tablet.
When wiring is complete, the tablet should be placed over the raised pillar of the base and the whole assembly secured by the cover-fixing screw engaging the threaded hole drilled in the pillar. Care should be taken to see that wires or cord conductors are not trapped between the different parts.

(b) Wall type - The cable to the station should lead into the instrument via the hole provided. Wires should be neatly arranged and terminated on the screw terminals provided.

Extension bells
Bells No. 56A should be used as extension bells, the bell coils being connected in parallel.

Requisitions
Complete instruments for new work or maintenance exchange should be ordered in the normal way. Many of the parts are non-standard and only the following individual items are replaceable:-

(a) The inset transmitter may be replaced by a Transmitter inset No 13.

(b) The handset cord may be replaced by a Cord, Instrument, No. 3/63A, Black, 42 in.

In all other cases of damaged or faulty parts the complete instrument should be changed.

Power supplies
The power for the system is derived from two 6 volt batteries, each consisting of four Cells, Dry, R 40, housed in a Box, Battery, No. 10. One battery is used for speaking, the other for signalling. The positive connections of the two batteries are commoned together. The batteries should be located as near the centre of the system as. possible, and wired to the nearest Box, Junction, House or Block, Terminal, No. 37A as shown on Dgm Q(L) 352.

TELEPHONE HOUSE No 100    5 STATION TABLE INSTRUMENT. INTERNAL. BLACK
TELEPHONE HOUSE No 101    5 STATION WALL INSTRUMENT. INTERNAL. BLACK
TELEPHONE HOUSE No 102    10 STATION TABLE INSTRUMENT. INTERNAL. BLACK
TELEPHONE HOUSE No 103    10 STATION WALL INSTRUMENT. INTERNAL. BLACK
TELEPHONE HOUSE No 104    15 STATION TABLE INSTRUMENT. INTERNAL. BLACK
TELEPHONE HOUSE No 105    15 STATION WALL INSTRUMENT. INTERNAL. BLACK

 
 
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Last revised: December 20, 2010

FM