Patent GB-284409-A (GB)
Title: Improvements relating to electric signalling systems
IPC: H04Q9/04
Filed: 1926-10-29
Abstract: 284,409. British Thomson-Houston Co., Ltd., Petch, H. S., and Wheatcroft, E. L. E. Oct. 29, 1926. Addition to 272,975. Tell-tale apparatus.-Relates to a telemetering system whereby the readings of several instruments such as 98, 100, 101 recording load, waterlevel, winding temperature or the like at a transmitting station, Fig. 2a, may be selectively transmitted to several indicators such as 97, 99 over lines 91, 46, 47, 41, Fig. 3a, common to all the instruments. The indications are telemetered as described with reference to Fig. 9b of the parent Specification, and the instruments automatically notch back to zero when out of use, as described. with reference to Figs. 11<b1> and 11<b11> of that Specification. The present Specification describes means comprising selector switches whereby the common signalling lines and relays may be appropriated to a given pair of instruments : thus the readings of the transmitter instrument 98 may be telemetered at the indicator 97, or the readings of either of the instruments 100, 101 may be telemetered at the indicator 99. In order that the instruments 97, 98 may be given possession of the lines, the key 95 at the indicator 97 must be depressed. The relays X, YI, WI, WT, YT then become energized, as described in detail below, and so long as they remain energized a 4-impulse cycle of operations is carried on by the relays GT. VT, GL, VI, the relays VT and VI serving to step round the arms 93a, 93<b>, 93<c>, 93<d> at their respective stations till the appropriate contacts are reached, whereupon the relay Z arrests the repetition of the cycle and operates the relay PI. On release of the key 95 all the relays except PI reset, and the relay PT is energized; thereafter, so long as PI and PT remain energized, the telemetering between the selected instruments proceeds as. described in the parent Specification. If the key 95 has released before the wipers 93 have reached the appropriate contacts, the wipers hunt round until they reach the end contacts, whereupon all relays reset permanently and the lamp 96 lights up. The parts YI, X, GL, YT, GT, 93<a>, 93<b>, 93<c> relate to the instruments 97, 98,. while YI<1>, X', GR, YT<1>, GT', 93<1> relate to the instruments 99, 100, 101. Preparation for action of selector switch. When the key 95 is depressed, the indicator relay X is energized through the contact 95b, extinguishes the lamp 96, and energizes (through GR2) the relays YI, WI (lower coil), which are held on through the armature YI1, the relay YI<1> being disabled at YI5. At WI3 a circuit is closed over the line 91 for the relav WT, which energizes the relay GT through WT1, whereupon GT energizes the relay at GT1, YT being thereafter held on through YT1. Reverting impulse cycle for operating selector arms. So long as the relays X, WI, YI, WT, YT are energized, as described in the preceding paragraph, a repeating cycle of impulses occurs between the relays GT, GL, VT, VI as follows :- GT is energized over the line 46 through the armature VI1, and energizes VT through the armature GT2. A reverting impulse is sent to GL through the line 47 and armature VT1, and GL then energizes VI through the armature GL2. The energization of VI breaks the circuit of GT over line 46; consequently GT and therefore VT are reset and the circuit through GL and the line 47 is broken by VT; consequently GL and therefore VI are reset, and the resetting of VI reenergizes GT so as to start the cycle again. The ratchet relays VI, VT at each operation move their respective arms 93a. 93b, 93<c>, 93d, one step. Arrest of switch arm at selected contact. The wipers 93a, 93b, 93c hunt round till the wiper 93b, Fig. 3<a>, reaches that contact which is in series with the contact 95a of closed switch 95 of indicator 97. If the indicator pointer be not at zero the contact 107 is open and the wipers continue to hunt until zeroization of the indicator has closed this contact. Provided that it be closed, a circuit is established through the contact 95a and wiper 93b to the hold-on relay Z, which energizes the relay PI and pilot lamp 84 through armature Z5, and by breaking at Z2 the circuit through the line 46 and relay GT prevents the inauguration of a fresh reverting impulse cycle. The key 95 may now be released so that the relay X resets followed by the relays YI and WI, by the relay Z whose hold-on circuit is broken at WI4, by the relay WT whose circuit over the line 91 is broken at WI3 and at Z2 in parallel, and by the slow release relay YT. The relay PT, Fig. 2a, is energized on the resetting of WT through contacts WT3, wiper 93a, and contacts YT3 which remain closed for a short interval owing to the relay YT being a slow release relay. All the relays being now reset except PI and PT, which remain operated, telemetering proceeds as described in the parent Specification. If on the other hand the key 95 be released before the selector cycle has been completed, the wipers hunt round till they rest on their extreme righthand contacts.