A transmitter for repeatedly transmitting a measured value in the form of a digital signal through a two-wire transmission line, includes a receiving unit for receiving a digital command signal from a communicator through the two-wire transmission line, and a processor for sending out a response signal...http://www.google.com.au/patents/US4806905?utm_source=gb-gplus-sharePatent US4806905 - Transmitter for transmitting on a two-wire transmitting line
