Abstract: This invention relates to an arrangement for transmitting a digital supplementary information signal having a low rate with a digital data signal having a high rate. The insertion of the supplementary information in the data signal is based on the modification of the accumulative disparity of data signal as a function of the logic level of the supplementary information signal. According to a first embodiment, parity check words are periodically inserted in the data signal and have their accumulative disparity which depends upon the comparison of the desired parity indicated by the logic level of the supplementary information signal with the accumulative disparity of data digits between two successive parity check words.

Abstract: Monitoring system for a forward and backward link equipped with two way repeaters-regenerators comprises a monitoring station including means for transmitting through the forward link information data and a low frequency control signal and for receiving through said backward link information data and supervisory words respectively monitoring the performance of the repeaters-regenerators and identifying errors made therein. In each repeater regenerator a supervisory word is stored in a shift register and advance pulses for said shift register are obtained by frequency division of the low frequency control signal. The supervisory word is completed by a start bit and a stop bit, and modulates the low frequency control signal. The modulated start stop supervisory word is transmitted to the monitoring station through the backward link.