PRIVATE OR PRIVATE BRANCH EXCHANGES
Designed for use as a private branch exchange, the N308A 50-line switchboard is similar to British Post Office type AT3796.
Drop type, hand-restored indicators, N4816D, are used for the exchange lines, and disc type, self-restoring indicators N4755M, for the extensions. Similar disc indicators N4752M in the keyboard give double negative supervision.
Exchange lines may be C.B. manual or auto, a dial being fitted for the latter.
Two keys "speak/ring" and "dial/ring-back" are provided for each cord circuit.
The board is matt polished and has a Bakelite micro-telephone with plug and jack connection also an "alnico" generator, a bell with cut-off key, and night extension keys.
Similar boards, N306A and N307A (illustrated) normally used as private exchanges, are
wired for exchange lines and have a common "dial/ring-back" key so that there is
only a speak/ring key per cord circuit.
N308A was sold to the GPO as their Switchboard AT3796.
Last revised: October 12, 2019