| 摘要 |
A model railway engine carries a loudspeaker which is connected via the running rails to an electronic circuit which drives the loudspeaker to produce sounds simulating a real engine. To achieve synchronization of the sounds with the rotation of the engine wheels, a light diode on the engine emits light which is reflected off the inside of a wheel of the engine onto a phototransistor. The reflecting surface is marked to produce the desired pattern of light pulses at the phototransistor, which is connected to the electronic circuit.
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