| 摘要 |
A model railroad crossing bell and flasher employs spaced photocell detectors along the model railroad track. A comparator receives the photocell detector output signals and upon detecting a train shadow provides power to a first oscillator which actuates a pair of light emitting diodes in alternate sequence. Simultaneously, the first oscillator provides power to a second oscillator of a different frequency than the first oscillator. The second oscillator attenuates the first oscillator output signal to create a ringing sound through a loud speaker.
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