LOUDSPEAKER INTERCOMMUNICATION TELEPHONE
Table telephone for use as master station on loudspeaking telephone systems.
N1745 shown to the right.
For side stations see N1720 and N1590.
|Code No.||No. Intercom Lines||No. Master lines|
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In case (c) an extra condition which must be catered for is that of communication between the two master stations. There are many ways of doing this but the particular requirements of each installation have to be carefully considered, as it is not possible to give good loud speaker reception at one station when speaking at a distance from the microphone at the other station.
The master station consists of a polished mahogany casework, the front of which is equipped with the necessary number of keys and lamps.
When a side Station calls up, a lamp associated with it lights and indicates the number of the station calling. The lever key mounted immediately below this lamp is then operated and the speaking circuit is completed. An audible call is also given by a low pitched buzzer in order to attract attention.
A sensitive microphone is mounted in the top left-hand corner and a warning lamp in the right-hand corner. To guard against the leaving of a key in the operated position after the completion of a conversation, the warning lamp remains lit during the time that any key is in the operated position. A side station is called by depressing the appropriate key to its full extent or ringing position. On release the key takes up a middle or speaking position.
For those who desire a really neat and inconspicuous arrangement, a three-unit master station has been designed with the microphone and warning lamp fitted into a neat and pleasing inkstand (N7699B shown to the right). The casework is of polished mahogany or finished in oxidized-silver or bronze. The key box may then be fitted in any convenient position within reach.
The side station instruments with intercommunication facilities are similar to our standard intercommunication telephones with the addition of one or two press buttons
and lamps. When a call is received from the master station, the buzzer is operated in the usual way and a lamp is also lit in order to indicate that it is the master station calling. The removal of the hand-micro and pressing the master station button establishes the connection.
Similarly, to call the master station the hand-micro is removed and the master station button depressed to its fullest extent. Should a side station be engaged when called by the master station, the lamp at the side station will light and attract the attention of the user.
Conference facilities may be obtained by the master station throwing the appropriate keys. The stations thus selected can then speak and also hear what the other stations are saying.
From the point of view of initial cost and future maintenance it is not desirable to use any type of valve amplifier, and the Ericsson system requires only the usual type of dry batteries for the signalling part of the system, and either a 6-volt accumulator or high capacity dry cells for the speaking part.
Taken from Ericsson Intercommunication Telephone Booklet No. 4G
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