Uniden’s Professional Series PRO510XL Heavy-Duty CB radio offers High-Performance Full 40-Channel operation in a compact rugged CB radio. Extremely popular for Industrial Commercial and Off-Road use. This PRO510XL operates on any of the 40 AM frequencies authorized by the FCC and its S/RF meter and red-lit LED indicators help you monitor activity at a glance. A built-in noise limiter and ANL switch and squelch control fine-tune performance and eliminate noise and the front-positioned 4-pin microphone has an extra-long coiled cord for convenient use. While communicating flip on the ANL (automatic noise limiter) to help eliminate background noise such as that from the car engine/etc. The squelch control also assists with eliminating noise. A superheterodyne circuit with phase locked loop technology assures precise frequency control. Built-in External Speaker Jack allows connecting to an optional external speaker. Included in the box: CB Radio Microphone Mounting Hardware Mounting Bracket User s Manual.