Wow... a blast from the past! If more than one container of those obscure receivers were sold, I would be surprised.
If your considering buying it, Dont!
If you already own it, it may pass through AC3, but unlikely to decode it. Look on the back panel as see if there is a RCA SPDIF or Optical Toslink connector. If so, you mighjt try connecting to a stereo amplifier to test if the AC3 pass through is active.