Patent GB-576790-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: H02J13/00
Filed: 1944-03-31
Abstract: 576,790. Remote control systems. STANDARD TELEPHONES & CABLES, Ltd., BOWSHER, E. A. H., FONESCA, M. M. d'ASSAS-, and WARD, H. J. March 31, 1944, No. 6003. Addition to 514,991. [Class 40 (i)] The parent Specification describes a remote control and/or supervisory system, wherein a plurality of substations is connected by a common line to a central control or supervisory station, said control and/or supervision, after connection between the control and selected substation is established, being effected by continuous reciprocal interchange of impulses between stations the impulses being effective to prevent other substations from having access to the line. Whereas in the above specification the control and/or supervision was effected by increasing the length of one impulse, the present invention lengthens a plurality of impulses, thereby guarding against false operation due to accidental electrical disturbances &c. Fig. 1 shows the control station and Fig. 2 the substation. In Fig. 1 operation of the selection circuit CSC in a known manner sends out impulses over the common line L1, L2 to select a particular substation having selection circuit SSC, and selects for supervision and/or control a particular apparatus unit (e.g. a circuit breaker), the later operation giving rise to the setting of switches SPC in Fig. 1 and SPS in Fig. 2. CSC provides initial temporary circuits for relays SA and PSC. SA operates slow release relay SR which takes over control of relay PSC. Selection circuit SSC in Fig. 2 initially operates slow release relay PSS after which control is taken over by relay PGS. The normal shuttlecocking takes place as follows. At the control station incoming pulses from the substation actuate either positively polarized relay CP or negatively polarized relay CN either of which operates slow release relay PGC. PGC operates slow release relay PGL. Termination of incoming impulse releases CN or CP and SA operates to send out a negative pulse, over line L1 L2, whose time is determined by the slow release of PGC. Operation of the "Close" Key CK operates the relays CR and TL. CR reverses the polarity of the outgoing impulse to line (i.e. sends a positive pulse). TL provides an alternative path for the relay SA via pgl1. Thus SA stays operated while PGC and PGL successively release so giving longer outgoing pulses. Operation of the trip key TK operates TL only, thus giving the longer pulses but not changing their polarity. In Fig. 2 normal negative incoming pulses operate the negatively polarized relay SN which operates slow release relay PGS. On release of SN at the end of the incoming pulse relay SAS operates during the slow release of PGS to send back a short pulse to the control station so maintaining the shuttlecock arrangement. SAS operates slow release relay SAR which operates relay X. A long negative pulse from the control station releases SAS long enough for SAR to fall away. SAR released operates relay Y and changes operating circuit for X. X and Y operate relay LP and TLS which lock over auxiliary coils. At the termination of the incoming pulses SAS again operates and pulls up SAR which releases X but keeps Y operated. The next long pulse again releases SAR which now releases Y and so completes a circuit for the tripping contactor TC. Similarly long positive pulses operate for the closing contactor CC, relays SP and CRS operating instead of SN and TLS respectively. The contact breaker has auxiliary contacts IC so that when the breaker is closed relay JP operates and locks. On release of SAS JB operates relay PP whose contacts send out positive or negative pulses to the control station according to whether it is operated or not. These operate CN or CP (Fig. 1) to complete circuits for either the unlatching coil U or the latching coil L of relay OL so to light a green or red lamp, thus giving information as to the state of the breaker. Relay JB cannot release until SAS and PP are operated. If the breaker is closed on a fault and automatically trips, JB operates and locks. PP having operated when SAS was released stays operated until SAS operates thus giving time for a single positive pulse to be sent to line as a warning indication. If keys CK or TK are not depressed long enough so that only one long pulse is transmitted SAS cannot operate over lp5 up sas5 sar1 up and LP has its hold circuit broken at pgs2 up sas6 sar2 up and the relays TLS CRS Y and X resume normal conditions. An interfering long pulse at the control station releases SA long enough to release SR which in releasing PSC breaks down the shuttlecock action. At the substation it operates LP and CRS or TLS and as no subsequent pulse is received from the disconnected control station shuttlecock system, PGS releases followed by PSS which disconnects the substation shuttlecock system. It is suggested that a reset key for use immediately after pressing a control key could be made to operate upon this last principle.