47 CFR 95.409 - (CB Rule 9) What equipment may I use at my CB station?
(a) You must use an FCC certificated CB transmitter at your CB station. You can identify an FCC certificated transmitter by the certification label placed on it by the manufacturer. You may examine a list of certificated equipment on the FCC Web site at http://www.fcc.gov/encyclopedia/citizens-band-cb-service. Use of a transmitter which is not FCC certificated voids your authority to operate the station.
(b) You must not make, or have made, any internal modification to a certificated CB transmitter. (See CB Rule 25, § 95.425). Any internal modification to a certificated CB transmitter cancels the certification, and use of such a transmitter voids your authority to operate the station.