Patent GB-1067673-A (GB)
Title: Improvements in or relating to supervisory arrangements
IPC: H04Q9/10
Filed: 1962-10-25
Abstract: 1,067,673. Electric selective signalling. GENERAL ELECTRIC CO. Ltd. Oct. 23, 1963 [Oct. 25, 1962; Dec. 20, 1962], Nos. 40412/62 and 48122/62. Heading G4H. The invention is a supervisory system of the central station/remote stations type. Communication may be over lines or by wireless telegraphy. In the particular embodiment, there are twenty remote stations each containing twenty apparatus units to be supervised. In the normal quiescent state of the system, the twenty remote stations each apply a characteristic frequency, f 1  to f 20 , to the common set of lines to the central station. When an apparatus unit changes state at a station, the station removes its frequency from the lines causing the central station to (a) light a lamp corresponding to the remote station, (b) apply a frequency f A  to the lines to cause the other station frequencies to be removed from the lines, and (c) start a chain of relays operating in turn to effectively consider the remote stations in turn. When a " changed " remote station is reached (the jth station say), its characteristic frequency fj is applied to the lines by the central station and then removed. The central station then starts to send a frequency f B , to which the jth remote station responds by starting to send its frequency f j . Reception of this causes f B  to end, causing fj to end. The central station now starts to send a frequency f c  which causes the jth remote station to send a selection of the frequencies f 1  to f 20  (used before as station indicators) as indications of the states of its apparatus units, a frequency being present if the corresponding apparatus unit has not changed state. At the central station, these indications are stored in corresponding register units, there being 20 of these per remote station. Register units corresponding to changed apparatus each flash a corresponding lamp with an on : off ratio of 5 : 1. A fault warning lamp (at the central station) is also lit. When the operator presses an acknowledge key, the warning lamp goes off and the flashing lamp or lamps cease to flash but remain on. The central station now switches f B  on, f B  off, f c  off, f A  off to reset the remote stations, ending of f A  causing the remote stations to restore the station frequencies to the lines. The other remote stations are now considered by the relay chain mentioned (see (c) above). This sequence through the relay chain is repeated once as a check. If an apparatus unit which has changed, later changes back, an interrogation sequence as above occurs and the lamp in the corresponding register unit flashes with an on : off ratio 1 : 5, and a clear alarm is operated. When the operator presses the acknowledge key, the clear alarm and the flashing lamp go off. The operator can interrogate or control a particular remote station by pressing a corresponding key to select the station, and in the case of control press a selection of further keys to send a selection of the frequencies f 1  to f 20  to set corresponding apparatus control relays. In this case the frequencies may set each of ten relays in one of two states or alternatively set (or not) each of twenty relays. During set-up of the system for control, the central station sends a frequency f D  to the remote stations. Further modifications mentioned are: (a) provision of state-of-apparatus indicating lamps at the remote stations also, (b) switch-in of stand-by oscillators at remote stations if the frequencies f 1  to f 20  fail, (c) provision of an extra central station which can be prevented from interrogating and controlling remote stations by transmission of frequency f A  by the other central station, (d) dispensing with the remote station oscillators, the central station typically sending all the frequencies f 1  to f 20  of which a remote station returns a selection.