The DCPT-2500 is the transmitter/sensor included in the DCPA-2500 kit. You may purchase the DCPT-2500 to add a probe based sensor to an existing 2500 series system or to work with the DCR-2500 receiver. This probe based driveway sensor will detect any movement of metallic objects that occurs with the 10-12 feet of the probe you bury parallel to the driveway. The DCPT-2500 ships with 50' of wire that connects the probe with the transmitter box. This allows you to run the wire so you can hide the transmission box. You may also purchase the DCPT-2500 with 125' and 250' of wire. Call us at 800-366-7235 for details.