IMPROVEMENTS IN OR RELATING TO TELEPHONE OPERATORS DESK SETS

摘要

1,259,670. Telephone exchanges. SIEMENS AG. 17 Dec., 1969 [20 Dec., 1968], No. 61407/69. Heading H4K. An operator's desk set includes special service keys which change their function during successive operational sequences, indicators bearing a plurality of legends for each key and illumination means controlled by previous key operations and arranged to illuminate those legends appropriate to the current functions of the keys. As described each legend is on a separate indicator panel. The panels are illuminated by lamps controlled by interconnected relay circuits no details of which are given. Interlocks may be provided to prevent the effective operation of keys not applicable in particular sequences.