49 CFR § 220.37
Testing radio and wireless communication equipment
November 18, 2020
(a) Each radio, and all primary and redundant wireless communication equipment used under §§220.9 and 220.11, shall be tested as soon as practicable to ensure that the equipment functions as intended prior to the commencement of the work assignment.
(b) The test of a radio shall consist of an exchange of voice transmissions with another radio. The employee receiving the transmission shall advise the employee conducting the test of the clarity of the transmission.