Patent GB-467038-A (GB)
Title: Improvements in burglar alarm systems
IPC: G08B13/22
Filed: 1936-01-11
Abstract: 467,038. Burglar alarms. AGOSTINI, G. Jan. 11, 1936, No. 980. Convention date, Jan. 11, 1935. [Class 118 (i)] A burglar-alarm system controlled by secret contact combinations comprises a primary normallyclosed circuit fed from a source BP and two secondary normally-open circuits connected in parallel to an independent source BS, one of the two secondary circuits being independent of the secret control so as to afford permanent protection day and night. The protection contacts of the primary circuit may be put out of action by displacing the handle of the secret contact stud dial located in the secondary system, the alarm being given unless an electric lock has been opened first. Devices are provided for giving alarm signals at the relay station, for indicating the time and the locality of the attempted burglary, and for protecting the bell device and the casings enclosing the main elements of the system. The wires of the secondary system are enclosed in lead sheaths together with the wires of the primary circuit so that cutting of the cable gives the alarm. The apparatus is set by moving the arm 16 of the secret contact device CPP on to a particular stud, so as to close the primary circuit through the main relay RP. The opening of a door, window, &c. opens one of the contacts CP and de-energizes the relay RP, allowing its armature to close contacts 3, 4 and complete the first circuit of the secondary system, whereupon a relay RS opens contacts 6, 7 and closes contacts 10, 11, allowing current to flow for a short time so as to close the circuit of the audible alarms S1, SE, AS and of the stop relay of a clock H. At the same time a relay RVP is energized and closes contacts 30, 31 for the visible signal VP. Auxiliary windings 33, 32 for the relays RS, RVP are associated with interlocking armatures to maintain the closure of the alarm signal circuits after the other circuits cease to be energized, and until control knobs on the central casing are actuated. Should the burglar close one of the contacts CS, the second circuit of the secondary system is closed and the relays RS, RVS are energized to operate the audible alarms and the visible signal VS. The circuit of the secret contact device CPS is completed through the bolt of the lock for the central control casing. This casing, Fig. 4, is protected by spaced contacts 68, 69 normally held apart by an insulating rod 67 bearing on a lug 64 which bears against the wall 71 on which the casing is fixed, so that if the lid 66 is opened or the whole of the casing removed from the wall the contacts 68, 69 are closed to give the alarm. The casing of the alarm bell is provided with protective contacts 51, 51a connected by a wire 52 and included in the primary circuit, these contacts co-operating with contacts 50, 50a on the base. To prevent interference with the bell hammer by the interposition of a body, two spring strip contacts 55, 56 on the base close to an insulated part 57 of the hammer rod are connected in parallel with the contacts CS, so that when an attempt is made to move aside the hammer from the bell, the contacts 55, 56 are closed and the alarm is given. Similarly an alarm circuit is completed by efforts to tearoff or rotate the bell 58, which cause a metallic rod 61 rigid with the bell to meet a ring contact 60 fixed to the base.