| 摘要 |
Light barrier safety device having several light barriers (2-5) and a central unit (15) which drives the light barriers and generates a safety signal when at least one light barrier is interrupted. To provide such a device with a high safety standard and the least possible constructional expenditure, the central unit (15) contains a ROM-type step-by-step switching circuit (8) comprising a ROM (11), a subsequent stepped store (12) and a clock generator (13). At least some of the outputs (01-07) of the step store (12) are fed back to the input of the ROM and form a first subaddress. The receiver signals are applied to the other inputs (A0-A7) of the ROM and form a second subaddress. The storage locations of the ROM (11) determined by the total address from a first subaddress and second subaddress contain a cyclically repetitive predetermined sequence of bit patterns for the normal operating case and a storage content deviating from the predetermined sequence of bit patterns for the fault case. An information signal output (08) of the step store is connected to a safety signal generating device (10) which generates the safety signal on the basis of the storage content deviating in the fault case. <IMAGE> |
