GB980731A - Improvements in supervisory systems utilizing telephonic communication - Google Patents

Abstract

980,731. Substation supervisory equipment. SOUND DIFFUSION (SALES) Ltd. Feb. 10, 1961 [Nov. 26, 1959], No. 40230/59. Drawings to Specification. Heading H4K. In a system in which a change of state of equipment at a controlled location is arranged to call up a controlling station, the former emits a calling signal a plurality of times unless inhibited by the receipt of a signal from the controlling station. The invention is intended for use where the connection must be put through via a manual exchange. The equipment is of the same general type as described in Specification 868,768 using a recorded sequence of signals as follows: (1) an 8 kc. signal which establishes a line loop to the exchange, and connects the recorded output to the exchange; (2) an announcement of the controlled station's identity and that of the controlling station to which it is to be connected. A pause follows to enable the connection to be completed. (3) An 8 kc. signal which switches the exchange line to receiving equipment to which it remains connected for five seconds. ((4) An 8 kc. signal which restores the state to that of stage 1 whereupon the sequence is repeated several times after which a long 8 kc. pulse shuts down the apparatus and disconnects it the exchange line. The sequence of announcements may be suppressed, however, when an appropriate coded signal is received during the five second interval (3). The coded signal consists of a series of twelve pulses some of which are elongated. The pulses step a first switch having appropriate bank contacts connected to relays which are caused to operate if the corresponding pulse is elongated. If at the end of the sequence the relays are all up, then a further relay operates to suppress the announcement series and also to render the shut-down signal ineffective. The signals from the controlling station may now contain further impulses for effecting control operations. Thus the switch may be stepped by further short pulses until a further elongated pulse is received which transfers the stepping to a second switch. The signal continues until fifty pulses have been sent. Complementary contacts of the banks of the two switches are interconnected so that when exactly fifty pulses have been received a circuit is completed to emit a signal over a bank of the second switch to effect an appropriate control. One particular contact on this bank may be used for release of the equipment.