Patent GB-514991-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: H02J13/00
Filed: 1938-03-18
Abstract: 514,991. Electric signalling systems. STANDARD TELEPHONES & CABLES, Ltd., and WARD, H. J. March 18, 1938, No. 8417. [Class 40 (i)] In a remote control and/or supervisory systems of the type wherein a plurality of substations is connected by a common line to a central control and supervisory station, the control and supervisory operations, after connection between the central station and a selected substation is established, are effected by a continuous reciprocal interchange of impulses between the stations, the impulses also being effective to prevent other substations from obtaining access to the line. At substations in which the controlling supervisory equipment is not connected to the line 'the station selecting receiver in response to the reciprocal signals prevents normal operation and the usual interlock between such a receiver and the substation transmitter prevents the transmitter from operating also. Specification 397,118 is referred to. Operations intiated by control station.-The operator causes the transmission from equipment SCM of impulses which in known manner effectively operates only desired sub-station receiver SCS, and the operator then causes a finder switch CS to set itself on contacts corresponding to the sub-station device to be supervised or controlled whereupon corresponding signals are sent from SCM to the sub-station receiver SCS which repeats them to magnet SSM of switch SS. Supervisory key K1, K2 is then thrown, PSC and SA pull up and connect negative feed to the line (-ve on L1, +ve on L2). Relay SAC locks PSC. At the sub-station, a relay in SCS responds and operates PSS which connects the line to polarized relays PS, NS of which NS responds to the negative feed followed by PGS which locks PSS. The key operation at the control station is momentary, and on the relapse of SA, polarized relays PC, NC thereat are connected to the line resulting in the relapse of NS at the sub-station whereupon SAS pulls up and connects positive or negative feed to the line depending on the condition of the relay PP, PSS remaining held by SAR. If the feed is positive, PC, PGC and if negative NC, PGC pull up and meanwhile PGS at the sub-station falls back slowly and releases SAS which reconnects the polarized relays PS, NS to the line, the disconnection of the feed causing the relapse of PC or NC at the control station whereupon SA re-operates and connects up negative feed again. It will then be seen that signals are continuously sent to and fro, relays PSC and PSS at the control and sub-station being held by slow release relays SAC and SAR respectively so that equipments SCM and SCS are. disconnected from the line and the battery feed or polarized relays are connected 'thereto as the case may be. At other sub-stations however, these to-and-fro signals operate one or other of a pair of relays (not shown) in the equipments SCS whereby the circuits of the PSS relays are opened to prevent the battery feed and polarized relay equipment at these stations from being connected to the line. The signalling is terminated by the removal by the control operator of the battery connection to lead LE. whereupon the polarized relay NS at the sub-station is finally restored and other operated relays including PSS fall back to connect the receiver SCS to the line. Signalling conditions of equipment from substation.-Bank 4 of SSM is connected to signalling contacts such as AU1, AU2 of contact breakers so that JB is operated or not depending' on the condition of the breaker when selected as described in the preceding paragraph, so that PP is operated or not to control the polarity of the signals sent back. At the control station, PC or NC pulls up to operate latching or unlatching windings L or U of relay DLC over the finder switch CS to control indicator lamps Gr, Rd. Changing the condition of a contact breaker.- The operator having ascertained its condtion throws key CK or TK as required. At the control station, RG and GG have been operated by PSC and at the sub-station SAR has operated X. Assuming CK has been thrown to operate the breaker, CRC and CG pull up and when SA next operates it is held during the release period of RG to send a long position pulse to operate PS long enough to 'release SAS and SAR at the sub-station whereupon X is maintained operated and Y pulls up followed by CRS which locks up. When SA falls back the positive pulses of normal length are sent and SAS, SAR become operated again so that X is released, Y is held and the operate coil CCR of the breaker is energized over sssm1. The change over of the breaker changes the condition of relay JB which by operating PP changes the polarity of the impulses sent back from the sub-station to light the corresponding signal lamp. When key CK is restored, the various locking circuits of CRC are opened in response to pulses from the substation and negative pulsing is resumed at the control station. If the breaker requires to be tripped, key TK causes similar operations to proceed except that TLC is operated and the operating pulse is negative and trpping coil CTL is operated. Tap changing.-The last two contacts of the switches CS and SS control tap changers and corresponding contacts of bank CSM3 are connected to RP which operates in response to pulses from the sub-station after key CK or TK has operated CRC or TLC to release this relay immediately so that a re-operation of the key is required for each step of the tap changer.