Abstract: Disclosed is a frame processing device (10) for processing frames having a plurality of data bits, a plurality of flag bits and a plurality of zero bits inserted within the data bits to avoid there being a pattern of the data bits which coincide with the pattern of flag bits, the frame processing device (10) comprising a host interface (16) for receiving and transmitting said frames having a first data rate, an encryptor (22) and decryptor (28) for encrypting and decrypting the data bits respectively, a network interface (26) for transmitting and receiving encrypted data bits having a second data rate, and an adaptive first-in first out (FIFO) buffers (22 and 30) for compensating for the difference between said first data rate and second data rate.

Abstract: A clean air system a fan and a filter assembly for producing a flow of clean air and for discharging the clean air from an outlet towards a clean area. A Coanda effect device is located adjacent to the filter assembly about the whole or part of its periphery, and induces movement of air away from the flow of clean air. Any potentially contaminated air must thus overcome the outward flow of air in order to reach the clean area, thereby reducing the likelihood of contamination of the clean area.

Abstract: Protective equipment detects the existence of an unsafe potential (V.sub.2) between earth and mobile equipment such as a mobile cabin. A metal plate (14) is mounted below the chassis (10) of the cabin, and the voltage (V.sub.3) between the metal plate (14) and the chassis (10) is detected by an amplifier (16). The amplifier output feeds a threshold detector (18) which senses when the voltage (V.sub.3) reaches a level corresponding to a predetermined dangerous potential (V.sub.2) of the chassis (10) with respect to ground (12).