| 摘要 |
A light switching device has a transmitter for generating light, a control circuit for controlling the light transmitted by said transmitter and a receiver for receiving the transmitted light. The receiver generates an indication signal which varies with the intensity of the received light. The device includes a first comparator having a first input for receiving the indication signal and a second input for receiving a first reference voltage. The first comparator produces a first comparison signal having a first state when said first reference voltage is greater than the indication signal and a second state when the first reference voltage is less than said indication signal. A second comparator is also provided and has a first input for receiving the indication signal and a second input for receiving a second reference voltage which is different from the first reference voltage. The second comparator produces a second comparison signal having a first state when said second reference voltage is greater than said indication signal and a second state when the second reference voltage is less than the indication signal. A charge storage device, coupled to the first comparator stores a charge amount which varies based on the first comparison signal, wherein the storage device increases the charge amount when said first comparison signal is in one of the first and second states, and decreases the charge amount when the first comparison signal is in the other of the first and second states.
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