TELEPHONE No's N1740 - N1745


Table telephone for use as master station on loudspeaking telephone systems.

N1745 is shown pictured to the right.

Mahogany casework

For side stations see N1720 and N1590.

Code No. No. Intercom Lines No. Master lines
N1740 5 1
N1741 10 1
N1742 15 1
N1743 5 2
N1744 10 2
N1745 15 2

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A Loud Speaker Intercommunication Telephone System incorporating all the notable features of our standard intercommunication system with the addition of loud speaker facilities for one or two Master Stations.

Present day progress demands that persons holding important executive positions should not be required to waste time doing needless operations, and at all times they should have full access to records, files and important papers. Unfortunately, however, the use of the ordinary telephone limits the movements of the user it necessitates the use of one hand at least and thus prevents quick and easy access to papers and at the same time the making of notes.

In order to improve such conditions, the Loud Speaker Telephones have been developed, by means of which a person is not required to engage either hand while telephoning, incoming speech being received on a loud speaker and outgoing speech picked up by means of a sensitive microphone. This means that after a single operation of a key it is possible to move about in any average size office and carry on a complete conversation with any desired extension.

The essential qualities of such a scheme are, that the received speech shall be both loud and clear, and the microphone shall be capable of picking up a normal conversation from any part of the office. By very careful design of the circuit and components this has been made possible to a degree which is considered superior to any similar system on the market. In a quiet office the cone type speaker (noted for its clearness) can be heard 30 to 40 feet away, and the microphone will pick up at this distance without difficulty.

The following three systems are standardized :-

  1. A system consisting of a master station N1740 type and a number of side stations N1590 or N1594 type with communication only between master Station and side stations.
  2. A system consisting of a master Station N1740 type and a number of side stations N1720 type with full intercommunication facilities between the side stations.
  3. The same as (b) but with two master stations and side stations N1721, 3 or 5 and N1727, 9 or 31 types

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.


Code No.  Finish
N7699 Mahogany
N7699A Bronze
N7699B Oxidized-silver

Taken from Ericsson Intercommunication Telephone Booklet No. 4G 

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Last revised: February 27, 2021