BATTERY INTERCOMMUNICATION TELEPHONES
Pattern No. B575
Comprises the same parts as Pattern No. B570, with the addition of a Wall Rosette and Cord.
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.