| 摘要 |
A four-wheel anti-lock brake control has at least three wheel speed sensors, each having one side grounded. One sensor for a non-driven wheel is monitored to assure circuit continuity between the sensor and the control circuit. All the sensor outputs are monitored by a self-check circuit to detect any sensor malfunction and to disable the control in the event of a malfunction. The self-check circuit further disables the control if a substantially zero rear wheel speed is indicated during periods of substantial front wheel speed, thus preventing the occurrence of anti-lock brake cycling in the front wheels when the rear wheels approach a lock-up condition. The self-check circuit further disables the control when any brake modulator is not in its normal position prior to a request by the control for anti-lock operation. In each case, the self-check circuit will disable the control only after some predetermined time delay. Two different time delays are accomplished using a single timing capacitor. A circuit is provided to release the rear brakes briefly when and if the front brakes are released first by the anti-lock control.
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