NATIONAL TELEPHONE COMPANY
B570

BATTERY INTERCOMMUNICATION TELEPHONES

SECRET SERVICE

WALL SET

Pattern No. B570

Comprises - Hand Combination Transmitter and Receiver, Cord, Bell, Automatic Switch-hook, Relay, Line Selector and Ringing Key.

Produced in 5, 10 & 15 line models.

These are cheaper forms of the Secret Service Instruments, Patterns Nos. B560 and B565, but are in every way reliable and efficient and comprise all the advantages of the more expensive instruments.

Last revised: November 17, 2025