| 摘要 |
A circuit arrangement for monitoring a set of points is described whose drive is connected to a three-phase network via a four-conductor control cable. Power switches are arranged in the phases and current monitors are used whose signals are evaluated as bit patterns. After passing through the points, a test voltage is switched over to and bit patterns for continuous position monitoring are produced with power switches which can be switched off and on cyclically. According to the invention, the test voltage used is a direct voltage which feeds with one polarity (+) two combined phases (R, S) of the switched-off three-phase network (R, S, T, Mp) and with the other polarity (-) feeds the third phase (T) which is combined with the centre point conductor (Mp). The direct test voltage can be switched on by means of a semiconductor switch (9) as a function of the switching of the power switches (1 to 5) clocked in a test mode. In all three phases (R, S, T) and the centre point conductor (Mp), current monitors (Ü1 to Ü4) are arranged, of which at least the current monitors (Ü1 to 3) in the phases (R, S, T) are to be configured as D.C.-A.C. monitors with a wide current range. <IMAGE>
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