Closed loop binary digital communication system

Claim 1

Apparatus for interference resistant communication between a data source and a data sink of binary digital data messages where a message is made up of a train of discrete message elements where each message element consists of a binary one, or a binary zero, or a space, said apparatus comprising: a first station and a second station interconnected by a transmission medium, said stations being in the relation of data source and data sink, each of said stations comprising transmitter means for transmitting first, second, and third signal states which are assigned to represent message elements including binary ones, binary zeros, and spaces therebetween, transmit buffer means for holding data to be transmitted, receiver means for receiving message elements transmitted by the other sation, timer means for limiting the amount of time that will be used in attempting to transfer a message, comparator means for comparing transmitted and received message elements, filter means for enhancing those characteristics of the received signal which are not used for communication to which the receiver is sensitive, receive buffer means for holding message elements received and compared, and local controller means responsive to said timer means and to said comparator means to effect transfer of positively compared elements to said receive buffer and succeeding elements from said transmit buffer to said transmitter means; said first and second stations being operative in response to said timer means to reverse roles as data source and data sink when a predetermined time period is exceeded without completion of a message transfer.