ERICSSON
TELEPHONE No. N1670

This distinctive and registered design combines all the facilities of a small switchboard and an intercommunication system in one instrument. The case is of moulded Bakelite and incorporates a much improved type of micro-telephone rest which has been specially designed with a view to reducing the risk of breakage's. The interior mechanisms and apparatus are arranged to give maximum accessibility to all parts and the buzzer is mounted on the connecting plug so that it may be readily adjusted without interfering with the instrument. Each set is connected up to a system on the plug-and-jack principle. If required, a directory tray can be fitted under the base.

In order that the instrument should not be unnecessarily complicated, certain facilities were aimed at when designing, and the following have been achieved and standardised.

1. There is only one design of instrument for C.B. and automatic public exchanges, except that for the latter a dial is fitted.

2. Any instrument in an installation may be arranged as the master station.

3. Calls to or from the public exchange are secret. Local calls on the intercommunication system are non-secret.

4. The engaged test is provided on "busy" exchange lines.

5. Exchange lines may be "held", if it is necessary to intervene with another call.

6. Exchange calls can be transferred direct from one station to another.

7. Any selected stations can be arranged to supervise the exchange lines.

8. The master station controls trunk offering facilities.

9. Exchange calls may be barred to any station at the discretion of the master station.

10. The calling and clearing signals, at all types of public exchanges, are given direct from any station.

11. Any number or arrangement of the local stations can be connected for conference purposes.

12. An engaged test is given on stations engaged on exchange lines.

Taken from the Ericsson catalogue, edition No. 49

See also the article from the Ericsson Bulletin No.11

Last revised: July 23, 2025