GB717495A - Improvements in or relating to railway signalling systems - Google Patents

Abstract

717,495. Railway signalling equipment. STANDARD TELEPHONES & CABLES, Ltd. Feb. 8, 1952, [Feb. 14, 1951.] No. 3552/51. Class 105. Correspondence between the condition of a signal and its controlling member is checked by an electrical alarm circuit including a contact of a relay associated with the signal to indicate the position of the signal and a controller contact operated by the signal controlling member to indicate the position of said controlling member and an alarm device which operates only when the signal relay indicates a clear position and the controller contact indicates a danger position. As shown in Fig. i, in series with an alarm relay A are series-connected contacts r1, s1, t1, u1, of four signal repeater relays, each contact indicating, the condition of the signal with which it is associated, e.g. closed when the signal is at danger and open when the signal is cleared. Each of these contacts is bridged by a contact k1, l1, m1 or n1 of a routesetting medium, e.g. a sequence switch, which contact is closed when the sequence switch is in the position corresponding to the route or routes whose signal repeater relay contact r1 ... u1 is bridged thereby. The signal is cleared only after the sequence switch has reached such position, in which case contact mi, for example, is closed before ti opens and under these conditions retains the circuit of relay A closed. When a train passes the signal, this latter automatically restores to danger and contact such as t1 closes, followed by the sequence switch restoring to normal in response to the signalman and thereby opening contact mi. Thus the circuit of relay A is never interrupted except on a false clearing of the signal when its associated contact, e.g. t1 opens and the route contact mi will be open and the circuit of relay A interrupted. This relay releases and initiates an alarm and may effect other operations such as setting all signals to danger. A lamp N such as a neon lamp connected across the pairs of contacts such as m1, t1 glows when the contacts are open and indicates which of the signals is at fault. When the fault is cleared, contact, e.g. t1 is closed and the circuit returned to normal. In an alternative arrangement, the contacts of each pair such as m1, t1, are connected in series with each other and may be, with an indicator lamp, and with the alarm relay A, the series connected pairs of contacts being in parallel with each other. If a signal gives access to more than one sequence switch or other route setting medium, a normally open contact such as k1 ... n1 will be required for each switch. According to the Provisional Specification a key is connected in series with the chain of pairs of contacts and is closed when the system is to be used, the relay A locking the circuit over a front contact bridging the key. Specification 526,829, [Group XXXIX], is referred to.