The present invention relates to an amplifier system for satellites, in particular for radio-frequency amplifier systems incorporating travelling wave tube amplifiers and used in space repeaters. A guide rail arrangement directs the movement of the door leaf. The output side cell buffer section is provided with a device adapted to calculate a degree of congestion from logical queue length information fed from each of input side cell buffer sections and to judge which input side cell buffer section has its most congested state. An attenuated responsivity test path may be selectively coupled to the first optical switch. An isolator is disposed between each of the slide channels and the beams.