Hi,
if your calls goes directly to queue 4 calls = 4SC, if not, during transfer phase SC can increase for short time and goes back to 4SC if of course you have four calls going.
internally calls count also for SC, two extensions in internally call = 1SC

Yes, fourth stay waiting with MOH in the Q until one agent take the call, if a fith one try to reach your PBX, he can get busy tone if your sip provider is also 4 channels and send busy tone, some do , not all. So you may have just .....nothing.To clarify a bit, if all calls are directly routed to the queue, 3 are live (callers are speaking with staff), and a 4th comes in, it will land in the queue. It will not get a busy signal because it momentarily needs 5 SC?
Understood but does it really matter? I mean lets say there was no 'quirk' and it was a straight 4 calls = 4SC. You still have the risk of the 5th call getting rejected. So in either case 8SC would still be the recommendation. If they want to go down to the 4, then it's on them.
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