SEKERHETSANLEGGNING

• Main Authors: LEWIS J, GILMOUR W D
• Format: Patent
• Language: Swedish
• Published: 04.04.1977
• Subjects: ALARM SYSTEMS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDEDFOR ELSEWHERE; BASIC ELECTRONIC CIRCUITRY; CHECKING-DEVICES; CONTROL OR REGULATING SYSTEMS IN GENERAL; CONTROLLING; ELECTRICITY; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; GENERATING RANDOM NUMBERS; GENERATION OF NOISE BY SUCH CIRCUITS; GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING,BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN ANON-SWITCHING MANNER; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS ORELEMENTS; ORDER TELEGRAPHS; PHYSICS; REGISTERING OR INDICATING THE WORKING OF MACHINES; REGULATING; SIGNALLING; SIGNALLING OR CALLING SYSTEMS; TIME OR ATTENDANCE REGISTERS; VOTING OR LOTTERY APPARATUS

A security system controls admission of persons to protected areas. An authorised person carries in his pocket a token which generates at two discrete frequencies and when he approaches a door leading to the restricted area, a sensor of his presence sends an initiating signal to a control unit which examines whether the required discrete frequencies are being generated and are being picked up by inductive loops adjacent the door. If the correct signals are being generated the door is automatically opened but if not the door remains closed and an alarm may be given. The user does not need to take his token from his pocket so that the effect will be that the door will open automatically for authorised persons.