Intercom Table Telephone
For the dual line secret dialer system
Desk telephone device for the secret self-selecting system for 50 dual lines, of which 15 can be used as exchange lines

HK120
The telephone consists of:
Horizontal microphone RE 2002 with telephone cord RS 7021.
Reverser.
Two push buttons, one black and one red.
Ringer.

Weight 6.4 kg.

A cable, which is very flexible, connects the telephone set to a junction box HM 150. This cable is not supplied with the telephone set and is not included in the price. For normal cases, we recommend the following cable types:
RS 9915/82, when a maximum of 25 devices are connected and
RS 9915/132, when a maximum of 26-50 devices are connected.

If the self-selecting system is to be connected to a telephone exchange by means of one or more central lines, each such line is equipped with a relay device HK 530 or one of the system's devices HK 120 is replaced with a device HK 310-315.

The principle of the secret electoral system

Any of the self-selecting system devices can call and communicate with any of the other devices within the system.

If the auto dialer system is connected to a telephone exchange, the exchange can call the system and communicate with any of the system's devices.

Any of the system's devices can call and communicate with the telephone exchange.
The calling device is blocked the moment its handset is lifted.
The on-call device is not blocked until its handset is lifted.

Guidance on using the system

I. Calls within the system
If e.g. device 16 (see the diagram) wishes to talk to device 18, the selector is set to the number 18, the microphone is lifted and a signal is given, whereby the black button is pressed.

If the ringer in device 16 does not ring, this indicates that device 18 is currently busy. (Apparatus 18 naturally does not receive a signal either.)

If device 18 is free, ring the bells in devices 16 and 18. The microphone belonging to device 18 is then picked up and an answer is given.

Note: signal arrives at device 18 regardless of which number its selector is on, and device 18 can respond without the selector having to be moved to any particular position.

When the call ends, both microphones are put on hold.

II. Calls from a subscriber belonging to a telephone exchange to one of the self-selecting devices
When a signal from the exchange arrives at the device of the self-selecting system, to which the central line in question is connected (for example, device 16), the bell of the relay device belonging to the line rings. The selector is then set to the central line in question, the microphone is lifted, the red button is pressed and an answer is given.

Now if the central line wishes to connect, not with device 16 but e.g. with device 18, device 16 calls device 18 and announces this as stated under I and puts on its microphone again. Apparatus 18 then sets the selector to the central line in question, presses the red button and comes into communication with the central line.

(If device 18 were to set the selector on the central line, before device 16 put its handset on, device 18 will not enter the central line when the red button is pressed. In this case, in order to come on the central line, device 18 must wait for device 16 to put its handset on and then momentarily press the handset button and then the red push button.)

Note: During the time that device 16 needs to call device 18, the central line in question is blocked, so that no other device can connect to this line.

When the call is finished, the end signal is given by pressing the black button and the microphone is put on. (If the telephone switchboard, to which the self-selecting devices are connected, is built according to the central battery system, then the final signal is given only by putting on the microphone.)

III. Call from a self-selecting device to one of the telephone exchange's subscribers
The selector is set to any one of the central lines, the microphone is lifted and signal is given by pressing the black button.
If the device's bell then does not ring, this indicates that the central line in question is already busy.
If the line is free, the own bell rings and an answer is received from the telephone exchange, which establishes a connection with the desired subscriber.

Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 122 (1930) - Swedish translation

Also found in the Ericsson Catalogue 7th Edition (1923)

Last revised: June 08, 2024