By default it will alert all operators simultaniously. If you enable Forced Delivery it will round-robin the delivery:
Forced Delivery—select to make the queue a forced delivery queue. This makes an enquiry call
from the CTI Port to the next attendant handset in a circular, round-robin pattern. Attendants receive calls in a specific order (determined by the order in which they log in), and after the last receives a call, the first receives the next one. Attendants are skipped if they are still busy on a previous call.
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