Patent GB-269941-A (GB)
Title: Improvements in or relating to alarm circuit systems particularly fire alarm signalling systems
IPC: H04M11/04
Filed: 1927-04-25
Abstract: 269,941. Snyders, G. C., Gordyn, C., Kamp, J. van de, and Maitland, C. E. A. April 26, 1926, [Convention date]. Fire, police, and like alarm systems.-The lines of a group of call stations are led to a distributing station at which they are extended by automatic ' switches, such as line-finders, to trunks leading to a central station, the number of trunks being preferably less than the number of call stations. Selectors at the central station, set by successive sets of impulses, select lamp circuits to indicate the number and location of the calling station. The progress of a call is indicated by additional lamps at the central station, and faults on the a and b lines from the call station to the distributing station are indicated by separate lamps. Connection of calling station AGSt 431 by line-finder AS at distributing station VSt 1 to trunk HBW to central station. Current normally flows through the relays A, Q, B, A being not energized owing to the resistance of Q. The initial operation of the substation calling apparatus closes contact IK, thereby short-circuiting relays B, Q and energizing relay A, which causes a slow-release relay A1 to prepare the circuit of a slow-release relay A2. On the initial opening of the impulse contact 4J, relay A energizes relay A2 which causes magnet D1 to rotate the line-finder until the calling line is reached, when a test circuit is closed over relays P2, P1, Sa, this circuit including a lead of the trunk to the central station. If the trunk is faulty, a fuse in the test circuit blows thus preventing the connection. Control of indicator at central station. Successive sets of impulses, corresponding to the number of the calling line, are repeated by the relay A over the trunks a, b in parallel to the impulse relay J at the central station. A slowrelease relay K1, under control of relay J, causes relays VI, V2, V3 to bring the magnets D3, H, D2 successively und'er the control of relay J. Magnet D3 sets the switch W1 to select the hundreds lamp H4, say, and magnets H, D2 operate a co-ordinate selector W2 to select tens and units lamps Z3, E1, say, and to light a lamp LL 431, say, individual to the calling station. The insertion of the plug AbA to set up telephonic communication with the calling station causes relay L to close the circuits of the selected hundreds, tens, and units lamps. The depression of the release key AT causes relay F to restore the selector W1 and relays VI, V2, V3, and to open the test circuit including relays P2, PI, Sa thereby energizing the release magnet M of the selector W2, and restoring the line-finder. Lamps L1 - - L4 at the central station indicate the progress of the call. Indicating faults on calling line. An earth on the b-line de-energizes relay B, thereby lighting lamp Lr. An earth on the a-line de-energizes relay B to light lamp Lr and also energizes relay A, which causes relay A1 to light lamp Lg. Relay A prevents the energization of relay A2 and therefore the operation of the line-finder. Lamp Lw indicates a call through to the central station.