| 摘要 |
<p>Burgular-proof barrier providing protection against intrusions, comprising means for the transmission of signals modualted and coded by pulses in a predetermined code, means for the reception of the modulated and coded signals transmitted and means for recognising the predetermined code in the signals received, said recognition means supplying at an output a characteristic signal whenever the code is recognized, an alarm circuit whose input is connected to the output of the code recognition means and which supplies an alarm signal when the characteristic signal is absent, the code recognition means being constituted by a system of detecting pulses by coincidences and the modulated coded signals forming repeat pulse trains, wherein the system for the detection of pulses by coincidences comprises means for delaying as from the first pulse in each train, all the pulses preceding the final pulse in the train in such a way as to bring them into coincidence with the latter, and a logic state circuit for controlling these coincidences and which supplies the characteristic signal to an output forming the output of the detection system.</p> |
