During this test, the MMI’s Time Slot Interchanger (TSI) listens to a TDM timeslot. A digital count tone loops back in the TSI and onto another TDM timeslot without passing through any resource hardware. A tone detector port verifies the looped data. If the digital count is correct, then the test passes. The test is done for both TDM buses. Failures indicate that the TSI is unreliable.

This test runs on Multimedia Interface media module.