The WSD wall switch sensor is a reliable work horse with powerful passive infrared (PIR) detection technology as well as optional passive dual technology. This line of wall switch sensors are perfect for private offices, copy rooms, closets or any small enclosed space without obstructions. All of Sensor Switch wall switch occupancy sensors are easy to install and simple to use. Additionally, the WSD sensor has several on modes and switch modes that can be programmed using the front push button. For rooms with obstructions, the dual technology WSD PDT series sensor is recommended. Additionally, all WSD family sensors have a patent pending wiring method that enables them to function either with or without a neutral connection. WSD units come pre-configured for wiring without a neutral, however, if connection to neutral is required by code, contractors can convert the unit in seconds.