It Takes Real Smarts to Network Every Switch
Virtually all electrical devices, fixtures, and appliances require an electrical connection consisting of two wires: The Line wire provides the source of electrical current, while the Neutral wire provides its return path. Electrical appliances require both Line and Neutral wires to operate.
For most lighting fixtures, the Line wire is cut and a wall switch or dimmer is inserted in the circuit at that point. In many homes, however, builders use a wiring simplification where only the Line wire, or “leg”, is run through the walls to the switch or dimmer — the Neutral wire is present only at the light fixture itself. This wiring style is called switched leg.
For designers of home automation products, switched legs have been a major stumbling block, since the most obvious location for adding home automation controls is in place of — or integrated into—existing light switches and dimmers. When the Neutral wire is missing, the traditional solution has been to rewire the circuit. But bringing the missing Neutral wire to the switch location, or bringing both Line and Neutral wires to a new location, means homeowners must tear into their walls or simply give up part or all of their automation plans.
Attempts to design two-way control devices that can be wired into a switched leg have until now been unsuccessful. Powering them demanded enough current that the lighting on the circuit would glow slightly, even when switched off. What's more, electrical noise generated by dimmers or the fluorescent light ballasts that often share the same circuits would disrupt the two-way communications between the control and other devices on the network. Our first-generation switched-leg technology enabled reliable, bidirectional communications over switched-leg circuits using incandescent lights. Fluorescent lamps, however, remained a problem.
Now, our second-generation switched-leg technology allows reliable, bidirectional communications in a switched-leg circuit with incandescent, halogen, and fluorescent lamps. This technology integrates a new power supply design with a more efficient way to couple the power line carrier to the electric circuit. In addition, a unique circuit automatically compensates for the characteristics of the lamp and ballast.
Our switched-leg technology works seamlessly with our popular PL 3120 and PL 3150 Power Line Smart Transceivers, which manufacturers have integrated by the millions into electrical monitoring and control systems worldwide. By using switched-leg technology, both new and existing homes and apartments can be automated quickly and inexpensively.