Desk telephones for the secret self-selecting system with switchboard for 50 dual lines

HK310 - HK315
The telephone consists of:
Horizontal microphone RE 2002 with telephone cord RS 7021
Reverser.
Two push buttons, one black and one red.
Ring-on flaps - one for each central line.
Connection terminals, which are covered.

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.

A relay device HK 660 or HK 665 must be combined with the telephone set.

This device is used if a secret self-selecting system, consisting of devices of type HK 130 (possibly HK 120 or HK 100*) is connected to a central telephone station by means of several central lines and the calls arriving from the station are to be distributed from one place to the other devices.

The device serves partly as a secret self-selecting device HK 130, partly as a switching station for the lines coming from the central station.

When a signal from the central arrives at the device, one of the flaps falls at the same time. The selector is then set to the number that corresponds to the fallen flap, the microphone is lifted, the red button is pressed and an answer is given.

Now if the central line wishes to talk to another device within the system, e.g. device 18, the selector is set to the number 18 and signal is given by means of the black button. If the bell does not ring, this shows that device 18 is currently busy. (Apparatus 18 naturally receives no signal either.)

If device 18 is not available, ring the bells in both the switchboard and in device 18. When device 18 answers, the switchboard announces that calls are waiting on central line No. 5 (for example), whereupon the flap is lifted and the switch's microphone is applied.

Apparatus 18 then sets the selector to central line 5, presses the red button and connects to central line 5.

If device 18 were to set the selector on the central line, before the switch applied to its microphone, device 18 will not enter the central line when the red button is pressed. In this case, in order to enter the central line, device 18 must wait for the switch to be placed on its microphone and then momentarily press down first the microphone button and then the red button.

When the call is over, device 18 gives the end signal by pressing the black button and the microphone is put on. (If the telephone switchboard, to which the self-weighing devices are connected, is built according to the central battery system, then the final signal is given only by putting on the microphone.)

Call connection from a self-selecting apparatus within the system to the central telephone station is obtained without the mediation of the exchange by setting the selector to any one of the central lines, lifting the microphone and giving a signal by means of 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.

* If self-selecting devices of type HK 100 or HK 120 are connected to the system, this should be stated when ordering the devices HK 310-315.

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: March 27, 2024