| 摘要 |
An 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), wherein the alarm element is constructed to retransmit a magnetic alternating field without an energy addition, this alternating field being received and detected by a receiver (3). The invention is characterized in that the alarm element (4) 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) and in that 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.
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