| 摘要 |
PURPOSE:To obtain a spark-advancing function with the use of a simple circuit arrangement, and to facilitate the adjustment of the rotational speed at which spark-advance is initiated, by rapidly charging an ignition timing control capacitor for a predetermined time period in a range of rotational speed exceeding the spark-advance initiating speed. CONSTITUTION:A switch means control circuit 6 detects the rotational speed of an engine and performs such control that a switch means 5a in a partially dividing ratio control circuit 5 is closed for a predetermined period when the rotational speed exceeds a spark-advance initiating speed. Further, when the switch means 5a is closed, a resistor R5 in a trigger signal supply circuit 4 is short-circuited to promote electrical charge for an ignition timing control capacitor C1 to advance a phase with which the terminal voltage of the capacitor reaches the trigger level of a transistor Tr2 in a shut-off control switch circuit 3, resulting in spark-advance of the ignition timing. Meanwhile, when the switch means 5a is opened, the charging time constant of the capacitor C1 is returned to its original value. Thus, it is possible to facilitate the setting of the spark-advance initiating speed.
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