Calls dropping


I have a system in, pure voip. No analogue / ISDN lines.

There are 5 people in the office and they make and receive around 100-200 calls a day.

However, about 1-5 times a day, a call is dropped. It might be incoming, it might be outgoing.

Where can I begin to troubleshoot this?

Could it be resources? The reason I ask is because it is running on a relatively low spec ‘green PC’.

Asterisk 1.4.13 / GSM Codec
Celeron 215 @ 1.33GHz / 512Kb Cache / CPU MHz 1333.468
512Mb RAM
Swap 0K used.

I just looked at ‘top’ for a few minutes and it peaked at %CPU = 4.0 and %MEM = 2.0

Feedback appreciated.