All Trunks Busy. A state in which all trunks in a specific trunk group are busy. May occur when all trunks are actually occupied with calls, or when some portion of trunks are artificially blocked by system user in periods of understaffing to minimize number of calls in queue.
A condition in which all the trunks in a trunk group are busy, usually triggering some kind of indicator or exception state within the switch. The condition, of course, means that any incoming calls to that trunk group would receive a busy signal, and users of the PBX would not be able to initiate any more calls on outbound trunks, until one or more of the trunks in the group is released.
All Trunks Busy. When all trunks are busy in a specified trunk group. Generally, reports indicate how many times all trunks were busy, and how much total time all trunks were busy. What they don't reveal is how many callers got busy signals when all trunks were busy.