| 摘要 |
1,024,201. Burglar and fire alarms. L. B. HEISER. Sept. 7, 1962 [Sept. 7, 1961], No. 34431/62. Heading G4N. [Also in Division G1] An alarm system comprises a pair of terminals for connection to a battery or other D.C. source, a sensing arrangement connected to one of the terminals through a capacitor so as to be responsive only to voltage changes at the terminals, the sensing arrangement including a unidirectional conductive device of such polarity as to cause the sensing arrangement to respond only to decreases in voltage across the terminals, the sensing arrangement being such as to initiate energization of an electrically actuated alarm in response to decreases in voltage. The system may be used in a burglar or fire warning arrangement fitted to a vehicle. When the interior, bonnet or boot light of the vehicle is operated by means of one of the switches 26, 28, 30, 32, 34, 36 a load is put on the vehicle battery 10 causing a reduction in its output voltage. This instantaneous drop in voltage is used to actuate the warning system 40 of the invention when this has been set by closing the switch 64. The drop in voltage is amplified through the transistors 42 and 44 and the current, surge through the coil 60 operates the relay 62. This causes the contacts 65, 66 to close, so that current will flow through the relay continuously, and also closes the contacts 68, 72 and 70, 74 to bring into operation the horns 75, 77 and the lights 80. A flasher arrangement 82 in the circuit causes these to operate intermittently. The arrangement 40 may be contained in a box situated close to the battery inside the bonnet. In order to activate the circuit the bonnet must first be opened (in order to reach the switch 64), but closing it thereafter will not set off the alarm since this responds only to decreases in voltage. To detect fire, thermally operated switches such as 90 positioned in strategic positions in the vehicle may be arranged in parallel with the bonnet or interior lights. The system may also be used to determine the state of the battery, since the battery must normally bias off the transistor 44 through the resistor 55. If the open circuit battery voltage drops, the battery will fail to provide this bias and the circuit will be activated to set off the alarm. |
