10-20%: Beltpack is unusable – replies are garbled and data issues mean that key response is very slow.

When in Menu mode on a connected CellCom beltpack, scroll to the View Status icon and press enter, then scroll to the Connection Info Icon and press enter.  This will open the connection info screen as shown below:

Open

The RS or RSSI number will fluctuate from a minimum of 0 to a maximum of 50 ideally as the user walks through the antenna coverage area and may even fluctuate as the user stands still.  As a rule of thumb the best system performance will be obtained when the signal strength remains at 30 or above.  if the signal strength falls below 30 the beltpack may start losing audio or experience noisy audio bursts.  This usually indicates that the beltpack is starting to reach the operational limit of antenna coverage.
00-15: Unworkable audio quality: Calls may be heard but will suffer from digital noise
          and garbling. Replies will be difficult, and keys may not respond.
15-20: Typical values when walking out of range. Cues will usually be heard, but
          replies will have digital artifacts and glitching.
20-25: Acceptable values for short periods (such as walking between coverage zones).
25-30: The lowest acceptable values for consistent communications. A Clear-Com
          engineer will attempt to position antennas so that this is the lowest level seen.
30-50: Great communications, no drop-outs, clear audio, no glitches.

The Error rate or ERR number indicates the packets of audio which are lost or corrupted.  When this number exceeds a few percent the user may start hearing audible audio breakup. 
A high RSSI and high Error rate may indicate that there is another RF system causing interference with the CellCom beltpack and base station. 

0-5%:     (transient): Some digital glitches will be heard, but communication will be uninterrupted.
5-10%:   Audio quality is badly affected but the user is mostly intelligible.