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 .