| 摘要 |
A light-controlled, electrical light switch for supplementing or as a replacement for the light switch which can be found in all living rooms makes its manual operation on entering or leaving the room superfluous. The invention consists of a special light barrier having a light transmitter and two light receivers, as well as an electronic evaluation circuit for driving a switching relay. The light receivers, which are arranged laterally offset in the direction in which people move, recognise both a person passing through and the direction in which that person is passing through. The evaluation circuit counts, balances and stores the number of occasions when a person passes through. Each occasion when a person passes through triggers a counting pulse which causes a binary counter to count upwards or downwards by one step in the correct direction depending on the direction which is identified. In consequence, the counter level always corresponds with the number of people in the room. The signal "counter content greater than or equal to zero" controls a switching relay whose switching contact is connected in series with a conventional light switch or completely replaces it. Figure 1 shows the arrangement of the light transmitter and the light receivers as well as the logic signal patterns which result for a) "coming in" and b) "going out". <IMAGE>
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