4T Power Systems DeWALT *XR 20V Battery Dock The 4T Power Systems Multi-function Remote Control Trailer Light and Brake Tester with Volt/Ammeter is designed for RVs, trailers, and campers with a 7-blade RV Plug. This item includes 2 remote controls for trailer lights, a brake tester, and Schwintek control with a Volt/Ammeter, all in one convenient unit. There are two power options for the tester: the Dewalt tool battery is available if the RV battery is low or not installed. Typically, upon connecting the 7-way trailer plug, the tester will power up if sufficient trailer battery power is available through the charge line or if the tool battery is installed and turned on. The tool battery will override the RV power, and the onboard buck converter is set to approximately 13.6VDC, the same as the RV Converter. The two included remotes activate the systems as follows: "1" will activate Trailer Brakes for 5 seconds. "2" will activate the TM (Tail/Marker Lights). "3" & "4" are momentary for left & right turn signals. "5" Back-up lighting. "6" will activate Brake lights and toggle the SAE Connector ON/OFF for testing furnaces, etc. Four Circuit breakers protect your RV: a 20-amp for electric brakes, a 20-amp for Schwintek & SAE, a 15-amp for lighting, and a 10-amp for Power Port/USB. Two power outputs include a Power Port and a PID/USB charger. Perfect for setting up a backup camera system. With the top-mounted switch in the Reversing position, the SAE connector can operate moderate-sized single-motor cables and through-frame slides. The two Schwintek connectors are counter to each other; one will turn the motor clockwise, and the other is counterclockwise. There is no logic to the system; it purely drives the motors at full power in either direction. Included Cables*: Two 5' intermediate single-pair Schwintek Cables for intercepting cables from the controller to the test box, and can be linked together. Two 30' single-pair Schwintek cables. These cables, when connected directly to the box, can reduce the installation time for a Schwintek rack system by about half. One 4" SAE with quick connectors *Approximate lengths The remotes cannot signal through the trailer, so aim under or around the unit. The large yellow remote must be turned on by pressing #1&2 for .5 seconds and will sleep if not used for 10 minutes. The Smart Battery Dock will warn when the battery is nearly depleted. My co-workers at our employer's RV Sales and Service shop in Western South Dakota have been using these testers for a couple of years now and have saved countless hours in troubleshooting and final repair times. I have also built one for a local mobile tech who uses it daily. Now it's time to share with the rest of our industry. I use this tool daily in many functions, from Lighting to Slide-out systems and bench testing a furnace, and I believe you will find it invaluable. With a 30-day warranty if the test box is unopened, this product is reliable and efficient for ensuring the safety and functionality of the RV before and while on the road. Perfect for anyone looking to enhance their trailer setup with a trusted and durable system. Tool Battery Not Included! This Device can only use standard DeWalt XR batteries, not compatible with the "PowerStack" line.