The general idea of a decoder system is to have one decoder for each solenoid (valve or head) and to have it close to the solenoid. This gives maximum irrigation control, minimum wiring, easy installation and simple documentation.
When multiple solenoids are to be activated by one decoder, or the multi-station decoders (ICD-200, ICD-400 and ICD-600) are to be used, cables need to be run between the decoder and the solenoids. Put the decoder as close to the solenoid as possible, and use a twisted pair between the decoder and the solenoids. Do NOT connect the solenoids together with a common. Always use one pair for each output from the decoder. If 2 solenoids are to be fed from the same decoder output, wire from the decoder to the first solenoid, and then to the second from the first. The solenoids are therefore connected in parallel to the decoder output.
In high lightning areas it is not recommended to have more than 100-150 ft/30-45 m cable lengths between decoder and solenoid. Longer lengths can be used but it always increases the risk or lightning damage to the decoder and solenoids. Suppliers now offer color-coded "DTS" (decoder to solenoid) wire pairs for this purpose.