Abstract: A tool for the supervision and/or hypervision of a set of systems of different security levels, the systems transmitting messages, includes a display system, and further includes, for each supervised network, at least one gateway for converting the messages to image data, said gateways transmitting said image data via a one-way video link to the display system, at least one of the supervised networks being of a higher security level than the area in which the display system is placed. The invention applies notably to the centralized supervision of several information systems when said systems are subjected to different security constraints.

Abstract: A channel board which simplifies wiring.Each channel board 30-31 comprises its own controlled carrier current generator for the formation of primary groups, and preferably also for the direct formation of the secondary groups from pre-modulated channels. The requisite carrier current is obtained by controlling the value of the divisor N in the frequency divider contained in the feedback loop. The control of N is effected for example simply by inserting the channel board into its location or by providing in addition with a selector plug, or by means of loaded shift registers.