| 摘要 |
A unit (6) plugged permanently into the video-output (8) of a data-processing unit (2) maintains video-signal supply to a monitor (3) only while a radio signal continues to be received by a loop-antenna (12) from a card (14) worn by an operator. The signal, possibly encoded, is transmitted from the card (14) by a transponder (15) in response to reception by the card (14) of radio-frequency, also possibly encoded, transmitted locally of the processing unit (2) from the antenna-loop (12). Video-signal supply to the monitor (3) from the video-output (8) is interrupted within the plugged-in unit (6) when the card-signal is no longer detected upon movement of the operator out of range of the antenna (12), and is not restored until the card-signal is detected again with return of the operator. Supply of data and control signals to and from the processing unit (2) may also be interrupted, and rather than leaving the screen (4) blank, the monitor (3) may be supplied during the interruption with video signals from the plugged-in unit (6) for message/pattern display. <IMAGE> |
