C MARKETING - INSTALLATION
HOUSE TELEPHONE SYSTEM No. 1
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
Division). Telephone, House No. 104 is shown to the right.
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.
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
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.
|Number of Stations
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.
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
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
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.
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.
Bells No. 56A should be used as extension bells, the bell coils being connected in
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
- The inset transmitter may be replaced by a Transmitter-inset No 13.
- 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
The power for the system is derived from two 6 volt batteries, each consisting of four Cells,
Dry R40, 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 Diagram 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
Made by British Ericsson (ETL).