Boris,
If you have only one port to take inbound calls and it is busy processing a call when a second call comes in then there is no available trunk to handle that second call until the first one finishes and frees up the trunk. Thus, the “All Trunks Busy” situation. The same thing will happen if you have 12, 24, or N number of inbound ports and N+1 call arrives. Just like when all you agents are busy and one more call arrives... the the Switch/ACD will put the call on hold until an agent becomes available. VH is basically doing the same… if VH does not have a trunk to process the call with it, it will route the call to the hold queue and bypass the VH call treatment. If it only happens on occasion, it’s probably OK. (the customer will "not" be offered the option for a call back and will be put on hold, to wait in line, just like VH wasn't there) But if it’s frequent (very likely with only 1 inbound trunk configurated) then you simply need to configure [b]more [/b] inbound trunks.
If you get "All trunks Busy" on the first and only call then there may be a configutration issue. However, you should expect "All trunks Busy" on the second call to a "one trunk" system. Just as you would expect to go to hold it the "one and only" agent was already busy when a second call arrives.
Andy