Final answer:
The ELT can be tested at two levels: built-in tests to check the internal circuitry and battery, and transmitter tests that confirm the device is able to send out a distress signal effectively.
Step-by-step explanation:
The two levels of testing for the Emergency Locator Transmitter (ELT) are built-in testing and testing the transmitter itself. The built-in test is designed to check the ELT's internal circuitry and battery status without radiating a signal. It ensures that the ELT is ready for deployment and is typically conducted by maintenance personnel. On the other hand, testing the transmitter involves a more comprehensive procedure that confirms the actual operation of the ELT signal. This test should be done according to the regulations which often require coordination with authorities, as it involves broadcasting a distress signal which should not be transmitted during non-emergency situations.