System for controlling polarity state of start-stop telegraph signal train

A system for controlling the polarity states of a start-stop telegraph signal train comprising:

• input terminal means for receiving said start-stop telegraph signal train;
• switch means connected to said input terminal means for reversing the polarity state of said start-stop telegraph signal train in response to a control input signal applied thereto;
• output terminal means connected to receive the output of said switch means for sending out said controlled start-stop telegraph signal train having the correct polarity state;
• timing means connected to receive the output of said switch means for generating first timing pulses and second timing pulses, each of said first timing pulses being included in a time slot at which the stop element of a character of said start-stop telegraph signal train is expected to arrive, at least one of said second timing pulses being included in a time slot at which a stop element after a predetermined number of characters from said first timing pulse is expected to arrive;
• decision means connected to receive said output of said switch means and said timing means for deciding the polarities of signal elements of said start-stop telegraph signal train in synchronism with said first timing pulse and said second timing pulse respectively;
• and
• control means connected to said decision means and said switch means for generating said control input signal and for applying it to said switch means only when the polarities of said signal elements of said start-stop telegraph signal train are decided as the A-polarity during both the decision operations by said decision means.