Digital two-wire irrigation control system

Encoding apparatus for use in an irrigation control system having a plurality of encoders connected to said encoding apparatus by a single pair of conductors, said apparatus comprising:

• digital logic means utilizing complementary metal-oxide-semiconductor logic, including
• multiplexer means for selecting for output one of a plurality of on/off signals supplied by a controller,
• clock pulse generation means for deriving clock signals from an alternating-current supply,
• digital counting means for generating decoder addresses to drive said multiplexer means,
• register means coupled with said counting means and with the output of said multiplexer means, for holding successive blocks of control information, each block comprising a decoder address, an on/off signal, and leading and trailing delimiting zeros, and
• gating means actuated by said counting means and said clock pulse generation means, for serially gating successive blocks of control information from said register means;
• and
• coupling circuit means connected with said gating means, for selectively suppressing current flow in one direction through one of the conductors from said encoding apparatus, in accordance with the contents of the successive blocks of control information from said gating means.

A digital two-wire irrigation control system, comprising:

• an encoder, including
• decoder address generation means,
• means for selecting on/off signals for transmission with decoder addresses, and
• means for encoding decoder addresses and on/off control signals onto an alternating-current power signal by selectively suppressing excursions of the power signal in one direction;
• a pair of conductors for transmission of the power signal, encoded with decoder addresses and on/off control signals, from said encoder;
• and
• at least one decoder connected to said pair of conductors and including
• rectifier means for generating a direct-current signal from the power signal, and for generating a data stream derived from excursions of the power signal in the one direction,
• electronic switch means for connecting the direct-current signal from said rectifier means to at least one valve solenoid,
• means for identifying said decoder, and
• digital logic means utilizing complementary metal-oxide-semiconductor logic for deriving the encoded decoder addresses and control signals from said data stream, and for operating said electronic switch means in accordance with those of said control signals accompanied by a decoder address equivalent to said means for identifying said decoder.