| 摘要 |
In a circuit for monitoring a two-wire line between a control component of an alarm system, on the one hand, and an alarm means exhibiting a load resistor, on the other hand, the two-wire line to be monitored, together with the load resistor, a series-connected diode and a parallel terminating resistor, form a measuring loop. The measuring loop is connected via a series resistor to a voltage source which generates a quiescent current in the quiescent case, which determines a particular loop voltage in the measuring loop. The loop voltage is connected to a measuring and evaluating device via a test terminal. To reduce the circuit complexity, it is proposed to give the loop current source and the load current source the same polarity and to arrange a voltage invertor in the test loop between the loop current source and one of the two two-wire lines, to the input end of which voltage invertor, which is connected to the loop current source, the evaluating device is connected at the same time.
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