Patent GB-439971-A (GB)
Title: Improvements in or relating to electric remote indicating systems
IPC: B61L21/06
Filed: 1934-06-18
Abstract: 439,971. Selective signalling. STANDARD TELEPHONES & CABLES, Ltd., GRIFFITHS, J. B., BROWN, A., SEARLE, A. M., and HYDE, G. A. M., 63, Aldwych, London. June 18, 1934, No. 18049. [Class 40 (i)] In a system for indicating at a main station the condition of a number of track sections of the kind in which each of a number of sub-stations comprises means responsive to a change in condition of a track section, and apparatus at the main station includes a contact for each substation, each of such contacts being connected in turn to a single circuit over which the condition of the sections is successively signalled, means are provided to ensure that after all the contacts have been connected to the common circuit a warning signal is given if any substation has failed to transmit its signal. In the system shown the two-wire line a, b is connected by a switch DMC to the section lamps of a track diagram in turn. Switches DMA, DMB, at each substation operate in synchronism with DMC, each switch having a characteristic position in which it connects condition-signalling apparatus to the line. When all the stations should have sent their signals, conditions are changed so that the synchronous switches which have so far been receiving stepping impulses from the main station receive an impulse from each of the substations in turn, if all switches are in their proper position. If the switch at any substation is out of position it fails to give the stepping impulse to the other switches and an alarm is given. Detailed operation. When a train enters or leaves the section associated with substation A, track relay TA (not shown), falls back or pulls up energizing BC which locks itself, unlatches or energizes TRA, and bridges the signalling line through rectifier RC1 to operate the starting relay ST at the signal cabin. The latter, which can also be energized by a local key then energizes SH which locks up and makes a self-interrupting circuit for a pendulum relay PM controlling an impulsing relay RD. RD at each operation reverses the direction of the battery connections to the line by connecting up SD which is thus operated in series with relays DS bridged across the line at each substation in series with rectifiers RC2. SD repeats the impulses to the cabin switch and the relays DS repeat them to the substation switches. In its 2nd position the cabin switch unlatches relay TCA which controls the truck diagram lamp corresponding to substation A and in position 3 it connects the energizing winding of TCA to the line to give it the opportunity to pull up over contact tra2. At the same time, TR energized over another bank of the substation switch unlocks BC. In subsequent positions the remaining diagram relays are first released and then put under control of the corresponding track relays. When all substations have been tested, the cabin switch energizes CP which locks up, releases the impulsing equipment, and replaces the battery connections to the line by an impulse responding relay DS. At the same time the switch at substation A energizes CD in series with all the relays DS. Relays DS at all other substations and at the cabin cause the operation of their stepping magnets and DSA at substation A shunts out CD to enable DMA to operate shortly afterwards. When DMA opens its springs, all the relays DS fall back and all switches take a step. The next step by all switches is similarly controlled by substation B and so on. When the cabin switch reaches normal it energizes TS which unlocks CP to restore conditions to normal. If CP is energized for an abnormally long period a thermal relay TH locks up and gives an alarm. This arrangement ensures that an alarm is given if any of the switches misses a step or takes a double step during the indication part of its cycle.