| 摘要 |
PCT No. PCT/SE95/00100 Sec. 371 Date Jul. 19, 1996 Sec. 102(e) Date Jul. 19, 1996 PCT Filed Feb. 2, 1995 PCT Pub. No. WO95/21431 PCT Pub. Date Aug. 10, 1995An alarm element forming part of an alarm system and constructed to receive a magnetic alternating field having the frequency F and transmitted by a transmitter (2). The alarm element retransmits a magnetic alternating field without an energy addition, this alternating field being received and detected by a receiver (3). The alarm element (1) has a circuit which includes a coil (L), a capacitance diode (D) and a resistor (R) in series in a closed circuit, and a capacitor (C) connected in parallel across the resistor (R). The coil (L) and the capacitance in the capacitance diode (D) form a resonance circuit having resonance at the frequency F when the voltage across the diode (D) is zero volts. |
