(a) No persons may use an ATC transponder that is specified in
91.215(a), 121.345(c), or §135.143(c) of this chapter unless, within the
preceding 24 calendar months, the ATC transponder has been tested and
inspected and found to comply with appendix F of part 43 of this chapter;
and
(b) Following any installation or maintenance on an ATC transponder
where data correspondence error could be introduced, the integrated system
has been tested, inspected, and found to comply with paragraph (c),
appendix E, of part 43 of this chapter.
(c) The tests and inspections specified in this section must be
conducted by --
(1) A certificated repair station properly equipped to perform those
functions and holding --
(i) A radio rating, Class III;
(ii) A limited radio rating appropriate to the make and model
transponder to be tested;
(iii) A limited rating appropriate to the test to be performed;
(iv) A limited rating for a manufacturer issued for the transponder in
accordance with §145.101(b)(4) of this chapter; or
(2) A holder of a continuous airworthiness maintenance program as
provided in part 121 or §135.411(a)(2) of this chapter; or
(3) The manufacturer of the aircraft on which the transponder to be
tested is installed, if the transponder was installed by that
manufacturer.