Abstract: Method for multiplexing inbound and outbound calls from a call center to improve the efficiency of call center agents since an idle agent can sometimes place an outbound call rather than wait for another inbound call. A parameter k is used to have an ACD agent place an outbound call instead of waiting to receive an inbound call. Specifically, if more than k agents in an inbound/outbound ACD call group are idle, and no calls are in the inbound call queue, then, in accordance with the present invention, callback or outbound calls are assigned to idle ACD agents until k agents are idle. For example, in a preferred embodiment of the present invention, callback calls will be assigned to an ACD agent before outbound calls. Note that, in accordance with the present invention, at any instant, at most k agents will be idle, because as soon as k+1 agents are idle, an agent will be assigned to a callback or to an outbound call.