NATIONAL TELEPHONE COMPANY
SET SECRET SYSTEM
WALL AND TABLE SET
This instrument is arranged for double line Intercommunication System and by special means absolute secrecy is ensured. It is impossible to tap the lines and it is also impossible to overhear by induction if properly twisted metallics are used.
Some or the chief
advantages, therefore, are as follows:-
The illustration shows the instrument arranged as a Table Set with the bell on the back. If required as a wall Set. the bell can be removed from the back and fixed on the bottom. The fixing screws establish the connection with the rest of the apparatus.
5, 10, 15, 20, 25 & 30 line models.
Taken from the 1903 Catalogue.
Last revised: July 07, 2020