Hobbico frequency checker automatically scans all 50 R/C frequencies in the 72MHz band and identifies those frequencies in use. Each frequency is shown by a dedicated LED. LED showing channel in use stays lit, and unit continues to scan. 300' (91m) range without external antenna, 1000' (305m) with external antenna. Prevents accidents due to unwanted Rf interference from other modelers' radio equipment. Fits easily in pocket or Flight Box. One year limited warranty.