Patent GB-408239-A (GB)
Title: Improvements in or relating to burglar alarm systems
IPC: G08B29/06
Filed: 1932-09-30
Abstract: 408,239. Burglar and like alarms. TIBBLES, H. J., Brodsworth, Blenheim Crescent, Leigh-on-Sea, TIBBLES, H. C., 68, Alderbrook Road, and RELY-A-BELL BURGLAR & FIRE ALARM CO., Ltd., 49A, Wilson Street, Finsbury Square, both in London. Sept. 30, 1932, Nos. 27176/32 and 20955/33. [Class 118 (i).] In a burglar alarm system comprising a plurality of normally closed alarm circuits, an alarm device is set in operation by the closing of a circuit upon energization of a relay, which relay is energized only when all the normally closed alarm circuits are broken. A testing circuit is completed by the closure of door contacts, and broken subsequently by the actuation of a lock. In one form of the invention, two relays 1, 4 having each a low resistance coil 2, 5 and a high resistance coil 3, 6 are provided, the coils 2, 5 being arranged in parallel circuits which are simultaneously closed by a push-button switch 11, thus attracting the armatures 20, 21. Subsequent actuation of the bolt 13 of a lock 14 first closes contacts 23, 24 to close simultaneously two parallel circuits energizing respectively the high resistance coils 3, 6, and then the bolt 13 moves away from the leaf spring contact 15 to break the circuits of the lower-resistance coils, the armatures 20, 21, however, remaining attracted. Next, the outer door of the premises is closed, whereby stud contacts 46, 47, 48, 49 engage contacts 50, 51, 52, 53 on the door frame, the wiring 54, 55 thus introduced into the circuits of the coils 3, 6 causing the two normally closed alarm circuits to be completed. At the same time additional door contacts 56, 57, 60, 61 complete a testing circuit through an audible alarm 64 and leaf spring contacts 69, 70, which may subsequently be separated by the movement of a key-operated bolt 41 which opens contacts 39, 40 and closes contacts 73, 74 to energize arelay 30, the armature 29 of which releases a pivoted arm 31, which thereupon releases the spring contacts 69, 70. The system is now set. Breaking of either of the normally closed alarm circuits will then operate both an interior audible signal 64 and a visible signal 95. Should both alarm circuits become broken, a relay 101 becomes energized, due to the closure of two series-connected switches 99 by the armatures 20, 21, and the circuits for an exterior alarm 107 and a remote alarm 113 are completed. To re-set the system, the bolt 13 is moved to move the contact 15 away from contact 25, thereby de-energizing relays 79, 101, and then a relay 116 is energized to release the armature 104 of the relay 101. Next, the alarms 64, 95 are rendered inoperative by tripping an arm 84 against the action of a spring 85 until it is engaged by the armature 83 of relay 79. The armature 115 of the relay 116 engages a notch 114 on the armature 104 and is thereby retained in the attracted position, until the armature 104 is attracted, whereupon the armature 115 drops into its lower position and locks the armature 104 in its attracted position, where it remains until a bolt 117 is moved so as to cause the armature 115 to be attracted. The various relays and other devices may be arranged in casings protected by a normally open or closed alarm circuit. Some of the alarms may be dispensed with or arranged at points remote from the premises. A time switch may be arranged to break the audible alarm circuit after a certain period and close the circuit of a visible alarm. A modified arrangement of circuits is described including mercury switches and inter-engaging armatures operated by the high resistance coils. Both the normally closed alarm circuits may include thermally-operated devices, such as fuses, to render the system sensitive in case of fire.