| 摘要 |
A traffic detector is disclosed in which an output is produced when a metal object is in proximity to a coil implanted in a roadway. The coil is part of a resonant sensing circuit and is excited by the same oscillator that excites a resonant reference circuit. The phase change between the two circuits caused by the presence of an object near the coil is passed by a balun transformer phase detector and fed to a level detector which produces an output when a predetermined signal threshold is exceeded.
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