Patent GB-302409-A (GB)
Title: Improvements in or relating to fire alarm systems
IPC: G08B25/00
Filed: 1927-09-20
Abstract: 302,409. Automatic Telephone Manufacturing Co., Ltd., (Lomax, C. E.). Sept. 20, 1927. Selective signalling apparatus.-In an electric signalling system comprising a central station and a plurality of branch stations directly connected thereto, when a plurality of branch stations signal simultaneously, an indication is given of each at the central station immediately, and further indicating apparatus is operated to indicate the signalling stations successively. Fig. 1 shows alarm stations 13, 13<1>, 47, at each of which the operation of the alarm considering 47 earths line 2 and inserts resistance in series with lines 1, 2, the former short-circuits and the latter reduces the current through relay 5<1> while series relay 15<1> is retained. The system is thus operative in the event of a short-circuit between the lines. In this relay group RG2 relays 5<1> operates to complete the circuit of lamp signal F47 and operates relay 16<1>. This operates relay 6<1>, which locks itself and energizes the open main relay 25. This causes relay 40 to start the code switch CS, Fig. 2. Operation of code switch. Armature 50 completes the circuit of a slow relay 53, which on operation energizes the motor magnet 32, this interrupting the circuit of relay 53, interrupts its own circuit and advances the wipers 30, 31 one step. This interaction is repeated until the wiper 30 reaches the contact 87 marked by the relay 6<1>. Then the code control relay 43 operates, locks itself, and inserts the relay 90 in the circuit of relay 32 so that each operation of this relay actuates bells BB<1>. At the same time relay 53 is cut out by armature 56, and the chain of relays 41, 42, 53 co-operates with the motor magnet 32 so that the speed of stepping is reduced. At contact 85 the relay 43 is shunted and restored so that relay 90 is disconnected, providing a pause between the first and second digits of the code. At contact 86 relay 43 is again energized, and the second digit is transmitted through relay 90, the wiper 30 meanwhile reaching the contact 88 marked by the relay 6<1>, shunts and de.energizes relay 43. When wiper 30 reaches contact 89 an impulse is transmitted to the motor magnet 62 of the code cut-off switch CCS, advancing its wipers 60, 61 one step. The relay group RG4 repeats the signal until the switch CCS reaches contact 59 to operate relay 65, so that the slow relay 66 and the relay 62 complete the stepping of the wipers 60, 61, relay 65 being locked meanwhile. Contact 59 may be multiplied and the bank of wipers 60 so wired to give a number of normal positions to the switch CCS and to secure repetition of the code. Restoration to normal. Relay 65 closes contact 69 operating relay 17<1> (Fig. 1) to open the circuit of relay 16<1>, the locking circuit of relay 6<1> and of main relay 25, and in addition provides a locking circuit tor itself. The return of the switch CCS to normal releases relay 66 and thus de-energizes relay 65. Prevention of interference. In the event of relay group RG<1> being operated from alarm stations 13 or 13<1>, the operation of relay 5 operates the lamp signal F13 but relav 6 is inoperative till relay 25 is de-energized when the previous code transmission is completed when the code signal corresponding to station 13 is transmitted. In the event of a break in the alarm circuit relays 5<1> 15<1> will be de-energized both lamps T47, F47, but the release of armature 8<1> prevents the operation of the code switch. Testing. The code equipment for each of the lines may be tested by operations of the keys K, K<1> while the trouble and fire lamps may be tested by the common key K<3> without operating the code sending switch. If the code.sending switch becomes defective the operation of key K<2> causes relay 70 to substitute another code sending switch for the defective one. A cross connecting block CCB is provided to enable additional lines to be connected or for changing the codes of existing stations.