| 摘要 |
A school bus safety device provides an engine status line wired to a voltage detection location. The voltage detection location is a point in the electrical system of the school bus which is typically at a high voltage potential when the engine is in operation, and is at the same potential as ground when the engine is turned off. An edge-triggered logic device, such as a flip-flop, receives the engine status line as a clock pulse input. In a typical application, the falling edge of the engine status line causes the output line of the logic device to go high, thereby driving an annunciator, such as a buzzer. Therefore, turning off the engine of the bus causes the buzzer to sound. The driver walks to th e rear of the bus and notices if any sleeping children are left on board. A key switch device, located in the back of the bus, is used to send a reset to the logic device, thereby turning off the buzzer. The driver then walks back to the front of the bus, double-checking to see that all children are off the bus.</SDOAB >
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