| 摘要 |
<p>A protective device for computers and the like, for preventing electromagnetical pick up, recording and unauthorized use of data from computers during normal operation thereof, and for protecting them against high energy transient disturbances taking place on the main A.C. power line. The device comprises a network filter unit (1) made up by a plurality of sections (19) comprising inductances (21) and capacitances (23), interposed between metal oxide varistors (27), and a masking unit (3), comprising a power supply (31), a white noise generator (33) and a wide band amplifier (35) emitting the amplifed white noise through an antenna circuit (61). The white noise, being completely random and unpredictable, is impossible to be decoded. The masking unit further comprises a self-checking and alarm circuit that works when the device gets turned on, ensuring the operator that the whole system is working correctly, remains active while the masking unit is on, and informs the operator through acoustic and optical signals if damages in the masking unit should occur. <IMAGE></p> |
