Pair of wireless Bluetooth transceivers to connect Limitimer PRO-2000 (timer) with any signal lights. One external 12V power supply is included. Second transceiver is powered through connection to timer. Connect up to 4 signal lights to receiver via on-board RJ45 jacks. Receiver provides both power and data to connected signal light. It has range about 300ft (75m). Up to 4 transmitter/receiver networks can operate in proximity via selectable channels.