The P5W1 is a control box for the Basic Probe. This system is housed in a white indoor plastic enclosure. This system is most commonly used for simple annunciation when a vehicle passes. This system is supplied with a wireless sounding system for inside the building. Transmission Range: 500 feet. The convenient plug-in chime receiver has four volume levels and 52 melodies. Up to 8 chime receivers can be used. Non-volatile memory means you can simply move the receivers from one room to another. The Probe is purchased separately.