DT Systems AddOn Collar for RAPT1400Expand your RAPT1400 to a 2 dog or 3 dog system. This AddOn collar allows you to expand your RAPT1400 to a 2 dog or 3 dog system. Or use it to replace a lost collar. R. A. P. T. Series collar units are equipped with MAXX Range 360 Antenna The embedded MAXX Range Antenna is woven into the collar strap and runs along the entire length of the strap, providing extended range without the drawback of an external antenna. Provides 360 degrees of signal