Uninterrupted automatic call distribution during failure and recovery of computer-telephony integration

In a computer integrated telephony call center where an adjunct host ( 160 ) normally controls enqueuing of calls ( 168 ) in call queues ( 120 ) of an ACD system ( 101 ) and corresponding call queues ( 120 ′) of the adjunct host and assigning of the enqueued calls to agents, the ACD system assumes ( 604 ) control over its call queues upon loss of the control by the adjunct host (e.g., upon failure ( 600 ) of the adjunct host). The ACD system flags ( 602, 606 ) all calls that are enqueued at the time of loss of the adjunct host control as well as all calls that the ACD subsequently enqueues as being under ACD system control. When the adjunct host regains its control ability, the ACD system stops flagging new calls, call queues of the host processor are cleared ( 702 ), and the adjunct host regains control ( 722 ) of enqueuing calls in call queues of the ACD and the adjunct host. But the adjunct host regains control ( 630, 730 ) of assigning calls from each call queue of the ACD system and the corresponding call queue of the adjunct host only when all flagged calls have been removed ( 628 ) from that ACD call queue by the ACD system. The adjunct host resumes assigning work to each agent only when the adjunct host has regained control ( 732, 734 ) of assigning calls from all call queues that are served by that agent. Failure and restoration of control by the adjunct host is thereby made transparent to calls.