04131882 is referenced by 80 patents and cites 7 patents.

A method and apparatus for the control of a number of valves in an irrigation system utilizing only two lines between a central encoder and a number of remotely located decoders. An alternating-current signal on the lines is used both to transmit power to the decoders and valves, and to convey control information in the form of decoder addresses and on/off signals represented in binary form by selectively clipping the alternating-current signal. The encoder includes timing and switching circuitry to effect temporary interruptions of the alternating-current signal, and to detect feedback signals transmitted from the decoders during the interruptions. At each decoder, the received control signals are recovered from the power lines, and each received decoder address is compared with one which identifies the decoder. When a match is found, the received on/off signal is employed to switch a valve and to initiate transmission of a confirmatory feedback signal. A portable operator, which may be connected to the power lines anywhere in the system, monitors the control signals transmitted from the encoder, and transmits special feedback signals which direct the encoder to perform functions selected at the portable operator.

Title
Digital two-wire irrigation control system with feedback
Application Number
5/644535
Publication Number
4131882
Application Date
December 29, 1975
Publication Date
December 26, 1978
Inventor
Vinod Panday
Pomona
CA, US
Michael D Hollabaugh
San Jose
CA, US
Agent
Fulwider Patton Rieber Lee & Utecht
Assignee
Clemar Manufacturing Corporation
CA, US
IPC
H04B 3/00
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