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(11) | EP 0 327 403 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Condition monitoring system |
| (57) A condition monitoring system for monitoring the condition of a two-position switch
(SW), e.g. in a car or other vehicle, is arranged to provide selective drive signals
to the switch and receive an input signal from the switch, the system responding to
the received input signal (IN) to select which drive signal is applied to the switch
so that little or no current is drawn from the system by the switch in either of its
positions (A or B). Thus in the position shown, a low drive signal is applied to switch
terminal (A) and a high drive signal is applied to terminal (B) and little or no current
passes through the switch to its common terminal (C): however if the switch is changed
to its other position a current passes through the switch from terminal (B) and a
high input signal is applied at IN; in response to this the system charges the output
drives to apply a high signal on terminal (A) and a low signal on terminal (B). In
this manner little or no current is drawn by the switch in either of its positions,
but at changeover a high input signal will flow until the monitoring system responds.
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