| 摘要 |
The circuit detects the presence of a capacitor (14) on the input terminals of the computer which are fed by an input feed (2). A capacitor (32) is placed across the input feed wires (16,18), and a signal injected from a signal generator (33). The signal injection is via a transformer (34) with one coil in series with one of the input lines (41). The second coil (40) is connected to one side of a logic detector (48). A comparison signal for the logic detector is fed straight from the signal generator.If the computer input capacitance is present, the loop impedance is low and the logic comparator receives two equal signals. If however, the capacitor is absent, the loop impedance is high and the logic alarm is set, commanding an alarm signal through an amplifier (52) and loudspeaker (54).
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