Indicator for the purpose of showing when a substation telephone is speaking with the Exchange (a condenser of 1/4 microfarads capacity Is connected in parallel with the indicator.) 3-way switch. Wall fitting with 300 ohm ringer. The frameworks of the telephone instrument and of the wall fitting are of enamelled steel. The terminals are enclosed.

The intermediate telephone is in connection with the Exchange or the sub-station respectively depending upon the switch being either to the left or to the right hand. If the switch is in it's central position, the Exchange and the sub-station telephone are in connection. The conversation can In no case be overheard. Signals from the Exchange or from the sub-station telephone are heard at the intermediate telephone independently of the position of the switch.

The switch should however under normal conditions be in either the left or right hand position; a signal coming from one of the lines will then ring the intermediate station only and not the other extension line; a signal from the Exchange will ring the 1000 ohms bell and a signal from the sub-station will ring the 300 ohms bell.

Total Weight: 6,55 kg.

Taken from the L. M. Ericsson Telephone Catalogue No. 1921

Last revised: October 13, 2019