Improvements in or relating to the remote control of dictation apparatus over telephone lines

摘要

936,814. Centralized dictation systems. WOLFGANG ASSMANN G.m.b.H. Sept. 15, 1960 [Sept. 21, 1959], No. 31834/60. Drawings to Specification. Class 40 (4). Apparatus for the remote control of dictation apparatus over telephone lines comprises a transmitter at a calling station for transmitting signals at a pilot frequency and at a number of control frequencies, a receiver at a receiving station connected through telephone lines to the calling station, dictation apparatus controlled by the receiver, means at the receiving station for transmitting signals at a reply frequency, and a switching device at the calling station responsive to the reply frequency for controlling the connection of the transmitter to the telephone lines. The switching device contains a tuned circuit, incorporating either valves or a transistor, and a relay which is operated on receipt of a reply signal at the reply frequency after the receiving station has been called from the calling station. Operation of the relay connects the transmitter to the telephone speech wires, but the connection is maintained only if the transmitter is generating signals at the pilot frequency. The receiver is so arranged that no control operation can be performed on the dictation apparatus unless both the relevant control frequency and the pilot frequency are received simultaneously, thereby preventing accidental operation by speech, all the frequencies used being within the audible range.