NATIONAL TELEPHONE COMPANY
BATTERY INTERCOMMUNICATION TELEPHONES
Pattern No. B560
Comprises - Hand Combination Transmitter and Receiver, Cord, Bell, Relay, Automatic Switch-hook, Line Selector, Ringing Key and Induction Coil.
5, 10, 15 & 20 line models.
The most important point in connection with this system
lies in the fact that only single wiring is required in the installation. The
instruments give absolute secrecy and freedom from interruption. A third party
cannot accidentally, or designedly, overhear a conversation. The line selector
can be left in any position after using.
Last revised: July 07, 2020