We have asked the receptionist to monitor and log the time it happens - we will then do a service call with the people that installed the CIX/CTX and see what they come up with.

I also have more information now on how this is setup.

The receptionist has 8 pool lines (digital - PRI).
Should all those lines be in use, we have 1 analog (POTS) that is used as an overflow.

It also happens every now and then that this line lights up and no one is calling on it, or the pool lines are not all used.

Will keep it coming as I get it.