Abstract: An error correction code data communication system scrambles and descrambles both non-coded data and coded data by using substantially the same code process at the opposite ends of a transmission path. The frequency of the occurrence of an error correction pulse in a decoder is monitored to set up synchronization for descrambling. The transmitter includes an encoder for adding a correction code to a data signal to be transmitted, and a scrambler for randomizing the data signal. The receiver includes a descrambler for descrambling the data signal which was randomized by the scrambler, and a decoder for correcting a code error responsive to the error correction code. The scrambler modulo 2 adds an output of a random signal generator to both an input data signal and an output data signal. The descrambler modulo 2 adds an output of a second random signal generator to both an input data signal and an output data signal.

Abstract: In an earth station (11), an amplifier (15) amplifies a pilot information signal with a variable gain. An up link pilot is thereby transmitted with a controllable transmission power. A beacon receiver (28) detects a level or C/N with which a beacon signal emitted by a satellite reaches the station. A pilot receiver (33) detects a level or C/N for a down link pilot radiated by the satellite in response to the up link pilot. A controller (37) controls the gain to keep a ratio between the levels or C/N's constant. For keeping a similar ratio constant, another station may transmit a transmission signal with a likewise controllable transmission power and receive the down link pilot together with a return signal radiated by the satellite in response to the transmission signal. Still another station may control a similarly controllable transmission power in consideration of an up link attenuation which is estimated from the level or C/N of the down link pilot.