HTS No. 2

HOUSE TELEPHONE SYSTEM No. 2
Description, Installation and Maintenance

General
This Instruction describes the House Telephone System No. 2. The telephone instruments are coded in the 500 series and are similar in appearance to the Telephone No. 706, except that the dial is replaced by a push-button unit. House telephones of the 100 series (see Q 3950) cannot be interconnected with 500 series House Telephones.

Facilities
The House Telephone System No. 2 provides intercommunication between two or more locations (16 stations maximum) without secrecy. Access to exchange lines cannot be given, and the whole system must be housed in one premises. Several conversations may be conducted at the same time and conference calls may be established between an number of stations.

Description
Table and wall instruments are available having 5, 10, and 15 push-buttons, these are suitable for up to 6, 1 1 and 16 stations respectively. A multiple cable corrects the instruments together and the 10v dc required for operating the system is obtained from a Power-unit No. 53A. The table and wall instruments cannot be converted from one to another. All table telephones are supplied with line cords but not with terminal blocks.

Wall mounted instruments are not supplied with line cords and should always be cabled direct. The telephone instruments are fitted with Handsets No. 3 but to ensure operation of the spring-sets an additional weight (Part 1/DWE/7) is fitted.

The wall variants can have the handset temporarily placed, on the handset rest, in an "Off Hook" position.

There are two diagrams in the Q series for the system:-

Q 361 Shows telephone instrument and wiring of instrument to terminal block.

Q 362 Shows cabling of system and explanatory diagram.

Method of operation
Each calling button has a 'normal press' and an 'overpress' position. After lifting the handset, the required station calling button is depressed to its full extent. This operates the buzzer at the called station. When pressure is released the button restores to the 'normal press' speaking position. At the conclusion of a call, replacing the handset will release any operated calling buttons.

Conference calls may be established between any number of stations. The initiating caller must call each required station in turn. The called party must then depress the calling button appropriate to the initiating station.

Numbering of stations
Stations should normally be numbered in sequence according to their position in the multiple cable. If, however, the subscriber has any specific station arrangement, stations may be numbered and wired in any order, but the most economical cable run should be followed. A directory card is supplied with each instrument, enabling each station to be associated with a person's name. It should be noted that when installations consist of 6, 11 or 16 stations, the additional station is called by utilising at each station the spare button corresponding to that particular station number. if the subscriber wishes he may unclip the calling button cover and remove the numbers provided, replacing them with a designation label to suit his own requirements.

Installation
Table 1 shows the types of telephone instruments together with the number of stations that can be accommodated and the cable required. If, at the time of installation, there is the probability that the system may require extending at some future date, a larger cable should be fitted initially.

TABLE 1

Siting of telephone instruments
Very damp or dusty situations are unsuitable for House Telephone Systems.

Cabling limits
The maximum cable length between the two extreme stations is 600 yards for 5 and 15 button instruments. This will be reduced to 300 yards if one or more stations has an extension caller fitted. The 10-button instrument is limited to a maximum cable length of 500 yards, or 200 yards if extension callers are used. This can be increased to 600 yards 300 yards respectively, by running an additional 2-wire cable connected in parallel with the power pair in the main cable.

Extension callers
In addition to the buzzer in the instrument either a Bell No. 56A or Buzzer No. 20B can be fitted as an extension caller, the choice being left to the subscriber. In each case the coils should be connected in series.

Maintenance
The following individual items are replaceable:-

Transmitter-inset No. 13C or No. 16.
Receiver-inset No 4T.
Handset No. 3.
Weight, Part I/DWE/7.
Cord, Instrument No. 1. 4/88AK, ..., 10 in.

Should any other components require replacement, then the entire instrument must be replaced.

Power supplies
The House Telephone System No. 2 is designed to operate from a 10v dc supply derived from a Power Unit No. 53A. If possible, the power unit should be located near the centre of the system rather than at one end, and should be connected to the system as shown on Diagram Q 362.

Introduced circa 1967.

Close up of press buttons.  The clear plastic covers are removable to allow the installer to change the numbers.  The numbers are paper.

Wall mounted version

Last revised: November 23, 2021