LOUD-SPEAKING CONFERENCE TELEPHONES
The Ericsson loudspeaking conference telephones have the following properties:
HF 110 & HF 120
The switchboard consists of a case of reddish brown polished birch mounted on a
nickel plated frame of welded steel tubes. A key with a corresponding indicator for each side station is fitted at the front of the apparatus. All parts such as transformers, DC bells, relay etc. are fitted inside the case. The case is fixed to the frame by means of four screws.
There are two types of the switchboard:
HF 110 for 10 lines,
HF 120 for 20 lines.
The switchboard is connected to the wall fitting by means of a flexible cable and in addition it is provided with an extra receiver which is connected when lifted, the loudspeaker being disconnected at the same time. There is also a press button for disconnecting the bell, should the manager not wish to be disturbed.
height 750 mm, width 535 mm, depth 450 mm, weight HF 110 17 kg, HF 120 19 kg.
A side station is called from the master station by throwing the corresponding
key in bottom position which will ring the bell of the side station. As soon as the key is released it returns to middle or speaking position. The speech from the side station is reproduced in the loudspeaker. The conversation is secret,
i.e. it cannot be overheard unless additional keys are thrown. When the master station is called from a side station the corresponding indicator is actuated; when the corresponding key is thrown the indicator returns to home position and communication with the side station is
The loudspeaker is of the moving-coi1 type and has a permanent magnet. It reproduces the speech in a pure and undistorted manner. It is fitted in a case of the same colour and material as the executive's switchboard.
height 380 mm, width 406 mm, depth 231 mm, weight 8.7 kg.
RC 2100 & RD 2110
The microphones designed for this system can pick up and reproduce even comparatively feeble speech, no matter from what part of the managerís room it comes. There are two types of micro-phones: RC 2100 in a case of wood and RC 2110 in a case of soapstone.
RC 2100 is fitted in a cover of wood of the same colour as the switchboard and the loudspeaker. It has a red warning lamp placed below the micro phone proper.
height 126 mm, width 133 mm, depth 77 mm, weight 1 kg.
RC 2110 is fitted in a cover of soap stone with a frame of dull nickel plated brass. A red warning lamp is placed in the top right hand corner.
height 131 mm, width 142 mm, depth 77 mm, weight 2.2 kg.
The red warning lamp lights up as soon as a key has been thrown on the switchboard. If after the conversation has been finished a key should not have been returned to home position the lamp remains lit, indicating that conversation in the managerís room may be overheard elsewhere.
Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 188 (1934)
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