The TR-2000BT Bluetooth Wireless Transceiver for Limitimer Systems from DSAN Corp. is designed to connect the Limitimer PRO-2000 speaker timer system (sold separately) with signal lights. It is powered by the included external power supply. You can connect up to four signal light units to a receiver via the RJ45 connectors. The receiver provides power and data to a connected signal light unit and can transmit up to 300' away. Up to four transmitter/receiver networks can operate in proximity via the selectable channels.