What exactly is a two-wire system, or as it is often referred to, a decoder system? Think of the last time you were caught up in peak traffic with the hundreds of other people all driving individual cars, mostly alone in their vehicles, and all trying to get to the same destination at the same time. This is akin to the expense, extra time and sometimes frustration of running hundreds of wires.
Now, imagine if we could all take the train. The train makes a stop near everyone's home for pickup, but takes them all to the same destination in a calm orderly fashion. The two-wire path is the train and each train stop is a decoder. Everyone has a short walk to the stop, but the overall cost to the destination is much lower now as well as any future costs.
A two-wire decoder allows control over conventional 24-VAC solenoid valves, often in larger numbers, over relatively long distances. By inserting waterproof encapsulated decoder modules prior to each solenoid valve as needed in a low voltage, direct burial two-wire path, it streamlines everything. A wire is cut wherever a station control is needed and the decoder wires are spliced into the path. The decoders are then connected to the off-the-shelf local standard 24-VAC solenoids for individual operation of valves.
Each decoder is uniquely addressed for both the signal for their address and the power required for solenoid operation, and each uses the same single pair of wires. Systems can cater from 24 through to hundreds of decoders, all of which can be individually operated. This allows the installation of many irrigation stations (or valves) down the same wire run rather than requiring separate power wire for each solenoid. Decoder systems differ from conventional wiring because they allow control of many valves over very long distances, with corresponding savings in wire and labor. However, the installer must invest in the decoder electronics themselves, which will be offset by some of the wire savings.
Like all new things, it takes a while for landscape contractors to trust new types of irrigation technology, so traditional ones will always have their place. However, over the last few years in particular, two-wire systems are becoming more and more popular in the irrigation industry with costs being reduced as more systems and more volume are introduced.
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