Abstract: A method is provided for checking the operability of protective instruction transmission systems in on-line operation in which at least two stations, particularly multi-instruction equipment, are connected to one another by transmission links and communication channels. The stations each comprise instruction input and output lines for checking the protective instructions and a first station controlling and checking of the operability transmits a test signal to a second station to be tested, the second station returning the signal to the first station unaltered. Upon receipt of the test signal, the respective inhibit of the instruction input and output lines is effected in the first and second stations. Simultaneously, the first station emits the first test instruction which the second station returns to the first station immediately after receipt and, therefore, effects the transmission of further test instructions in the first station.

Abstract: In a command transmission system, a maximum of n independent commands are supplied to a transmitter and are converted into different signals which are transmitted in series over a transmission line. When no command is present, a no-command signal is formed for transmission over the transmission line. When simultaneous commands are present, only command-associated signals are transmitted, cyclically and sequentially, over the transmission line, as long input commands are pending. At the receiving end of the transmission line, the signals are decoded and converted into signals which are manifested simultaneously on a plurality of output terminals.