These instruments are not suitable for working in pairs.
Cabinet work of well-seasoned walnut.
This particular type of telephone is known as the “Sub-Station” telephone. The term “Reply and Call” is incorrectly applied to the ordinary battery call telephones.
The circuit and construction, as well as the operation, are similar to the inter-communication telephones K7867 & K7888, except that they are without a radial selector, and without any means of inter-communication between sub-stations. The central station instrument can be any of the telephones K7867, K7888, K7907 & K7913.
This system has been designed to enable a manager or other official to obtain telephonic communication with certain members of his staff both ways, while the staff can have no communication with each other.
It is necessary to have six wires running between the central station instrument and every sub-station, i.e., 4 common battery wires (2 for the talking battery and 2 for the ringing battery), one common call wire, and a separate reply wire from each instrument.
Instruments fitted with induction coil and arranged for ordinary local or central battery circuits can be obtained for extension to existing installations at an extra charge.
Wall telephones, comprising K7670 carbon granule transmitter, K7631 “Watch” pattern electro-magnet receiver, auto-reset ringing key, automatic switchook, impedance coil and 25 ohm bell on tail piece. External metal parts oxidised copper bronze.
Weight 3 lbs. 8 oz.
Dimensions 10 x 7 x 5 ins
Cost in 1932 and 1935 was £3.0.0
Last revised: August 21, 2010