Slow Speed Data Messages (RSQ and Gateway Status) (thanks to the Northern Ohio Digital Interconect Group for these procedures):
After an over-the-air user unkeys, the repeater responds with a Slow Speed Data message that includes the repeater callsign, followed by the Received Signal Quality (RSQ) of the user's transmission, as well as the current connection status of the Gateway.  This message will scroll across the display of your radio after you unkey.
RSQ values range from 0 to 9, with 9 being the best.  RSQ values are derived from the quality of the incoming data stream rather than the actual signal strength, although having a strong signal into the repeater usually results in a good quality data stream.
The RSQ value is an average value over the entire transmission.  Short keyups tend to result in a low RSQ reading.  For a more accurate reading, key up long enough to say your call sign and indicate that you are testing.
The Gateway Status Message will read "Not connected" if the ourbound Gateway connection is idle.  The message will read "Connected to XXXXXXXX" when the outbound Gateway is connected to another repeater or reflector, where XXXXXXXX equals the callsign of the connected repeater or reflector.