voip troubleshooting

[srv1strat]

does anyone know how the voip channels are assigned on calls?
is channel 1 always used if its available then channel 2, then 3.
on each new call does it take the first available channel?
is there a way to id the channel a call is using?
is there a way to identify if there is a faulty channel on the vcm?
the reason i ask is we have 2 sites linked with 512 leased line using a voip line, with a vcm10 on each end. occasionally calls using the voip line are distorted on one end of the call. there does not appear to be a pattern except the call is always over the voip line & the distorted side of the call is always the same end of the voip line.
telco has tested the line & confirmed its ok.

thanks for any help

 

[IPGuru]

Turn on Developemant tracing I the system tab of System monitor

This will give additional options in the staus menu including 1 to monitor VCM channels real time.

also check that the dataswitches on the affected site are correcctly configured for DifServ QOS