Telegraph systems

Claim 1

A TELEGRAPH SIGNAL TRANSMISSION SYSTEM USING ONLY TWO SIGNALLING CONDITIONS, MARK AND SPACE, COMPRISING: A TRANSMITTING STATION; A RECEIVING STATION; MEANS AT THE TRANSMITTING STATION FOR DERIVING FROM A BLOCK OF SIGNAL ELEMENTS A PLURALITY OF GROUPS OF CHECK ELEMENTS, EACH OF WHICH GROUPS IS INDICATIVE OF A DIFFERENT PARTICULAR RELATION BETWEEN ALL OF THE MARKS AND SPACES CONTAINED IN THE SAID BLOCK OF SIGNAL ELEMENTS, THE CHECK ELEMENTS WITHIN EACH GROUP BEING DERIVED INDIVIDUALLY FROM SELECTED DIFFERENT GROUPS OF THE SIGNAL ELEMENTS IN SAID BLOCK; MEANS AT SAID TRANSMITTING STATION FOR TRANSMITTING THE SAID BLOCK OF SIGNAL ELEMENTS TOGETHER WITH THE SAID PLURALITY OF GROUPS OF CHECK ELEMENTS; MEANS AT THE RECEIVING STATION FOR DERIVING FROM THE SAID TRANSMITTED BLOCK OF SIGNAL ELEMENTS A SECOND PLURALITY OF GROUPS OF CHECK ELEMENTS CORRESPONDING TO THE GROUPS OF TRANSMITTED CHECK ELEMENTS ACCORDING TO THE SAME PARITY AND SELECTIVE GROUPING RULES AS USED AT THE TRANSMITTING STATION; MEANS AT THE RECEIVING STATION FOR AUTOMATICALLY COMPARING THE SAID SECOND CHECK ELEMENTS WITH THE CORRESPONDING TRANSMITTED CHECK ELEMENTS; AND MEANS COUPLED TO SAID COMPARING MEANS AT SAID RECEIVING STATION FOR INDICATING AN ERROR IN THE TRANSMITTED SIGNAL ELEMENTS, UPON DETECTION OF A DISCREPANCY BETWEEN THE SAID TRANSMITTED AND SECOND CHECK ELEMENTS.