The Wireless Photosensor (PCELL WRI) is designed to be ceiling mounted where one of the photovoltaic collectors is facing a window or source of light. The photosensor can transmit a signal to a receiver up to 90 ft away. The photovoltaic cell must receive at least 20 foot candles of light for several hours a day to charge the storage capacitor. A Wireless Receiver (GR2400 WREC) must be on the GR 2400 Bus within the transmitting distance.