| 摘要 |
PCT No. PCT/SE95/00548 Sec. 371 Date Nov. 15, 1996 Sec. 102(e) Date Nov. 15, 1996 PCT Filed May 16, 1995 PCT Pub. No. WO95/31862 PCT Pub. Date Nov. 23, 1995An arrangement for preventing disturbances in electronic alarm systems of the kind used in merchandise security systems. The alarm system includes an alarm element which is adapted to receive a magnetic alternating field transmitted by a transmitter, and also to retransmit a magnetic alternating field. A receiver is adapted to receive and detect the the retransmitted alternating field. An LC resonance circuit is located in at least certain pairs of electric conductors (5; 12, 13; 20, 21; 25, 26) in the alarm system between the system electronics (2; 16) and a receiver coil (1; 24), and alternatively also a transmitter coil (14). The resonance circuit is tuned to the working frequency or frequencies of the system to produce a high impedance on the conductor pair for current directed in the same direction in the conductors, thereby heavily dampening disturbance sources coupled capacitively, inductively, or resistively to the alarm system. |
