Patent GB-942921-A (GB)
Title: Communication system
Inventor: DELANOY DONALD BRIAN
IPC: H04Q9/14
Filed: 1959-08-26
Abstract: 942,921. Electric selective signalling systems. PYE Ltd. Aug. 26, 1960 [Aug. 26, 1959], No. 29213/59. Heading G4H. In a communication system, at least some of the information which is passed between two or more stations in the system is in the form of pulses of one frequency F 1  or another frequency F 2  representing the digits 0,1 of a binary code or the states of a two-state device, but only one of the stations includes generators for the frequencies F 1  and F 2 , transmission from any other station being achieved by re-transmitting one or both of the frequencies F 1  and F 2  received from said one station. Three types of such a system are described. Remote control system Figs. 1a, 1b. Pulses from a driving unit DU, Fig. la are fed to a counter in a coding device CD the output of each stage of which includes a switch so as to provide a serial train of coded pulses to a tone gate TG which is arranged to pass either F 1  or F 2  in response to each digit of the code group. A first code group may be used to select a remote station; and a second code group may be used to select apparatus e.g. a pump at that station. At the remote station selected, Fig. 1b, the second code group is converted to discrete D.C. pulses by filters FL1 and FL2, and tone converters TP. A counter in a scanning device SC is stepped on by each pulse received and serves to register the code group supplied from filter FL1 in store ST. A parity check is performed as disclosed in Specification 942, 927. The code group registered in the store is converted by diode matrix DM so as to select one of two pumps. One of switches SW 1 - SW 3  is closed at the control station so as to transmit a control signal comprising one or both of frequencies F 1  and F 2  and perform the corresponding control operation on the selected pump. A further frequency F 3  may be transmitted to reset the system, and the control signal may alternatively comprise a further code group. Continuously scanning alarm systems, Figs. 2a, 2b. Pulses from drive unit DU, Fig. 2a, step scanner SC and condition tone gate TG to pass both frequencies F 1  and F 2 . The or each remote station, Fig. 2b, includes filters FL1, FL2 whose outputs control the stepping of a scanning device SC through AND gate G3 so as to examine in turn the states of cold cathode storage tubes connected to alarm contacts being supervised. The sequence of signals obtained from scanning the storage tubes is applied to a tone gate TG so that for each combined pulse of F 1  and F 2  transmitted by the supervisory station, either F 1  or F 2  is returned as an indication of the state of associated alarm contacts. The signals received at the supervisory stations are entered into a store under control of the counter in decoder DC and an indication of the state of each set of contacts is given on apanel AP. The decoder DC is stepped one for each pulse of F 1  or F 2  received from a remote station, and a synchronism check is obtained by connecting stages of the counters in scanner SC and decoder DC to a coincidence gate. Frequency F3 or only Fl or F2 may be transmitted to arrest the scanning cycle. Telemetering system, Figs. 3a, 3b. A remote station and apparatus at that station are selected as in the system of Figs. 1a, 1b. The apparatus selected may be one of a number of meters ME, Fig. 3b, whose output is coded in device CD to produce a serial train of binary coded pulses controlling tone gate TG to transmit the corresponding train of F 1  and F 2  pulses to the supervisory station, Fig. 3a. At this station the received code group is stored under the control of the counter in a decoder DC, converted from binary to decimal notation in diode matrix DM and displayed on a panel DA. Specifications 942,922, 942,923, 942,924, 942,925 and 942,926 also are referred to.