No persons may use an ATC transponder unless, within the preceding 24 calendar months, the ATC transponder has been tested and inspected and found to comply with requirements described in Attachment 30.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 requirements described in Attachment 30.The tests and inspections specified in the preceding 2 paragraphs of this article must be conducted by either:1. A certificated repair station properly equipped to perform those functions and holding:a) A radio rating, Class III;b) A limited radio rating appropriate to the make and model transponder to be tested;c) A limited rating appropriate to the test to be performed;2. A holder of Air Carrier certificate as operated in accordance with provisions set forth in Chapter 2 or Chapter 3 of these regulations who holds an approved continuous airworthiness maintenance programme; or3. The manufacturer of the aircraft on which the ATC transponder to be tested is installed, if the ATC transponder was installed by that manufacturer.ATTACHMENT 30 ATC Transponder Tests and Inspections.pdf