The number of lines will always be more and it is usual to mantain a 1 agent to 3 line/trunk ratio. In an inbound environment the idea is to service some customers through IVRs and to put some people in a que for a reasonable time. In one of our contracts at Voxel for an inbound customer support; the peak time volume is so high and the average call length is relatively small that even a 1:3 ratio doesnt seem enough.
If the line ratio is one-to-one then the new caller will get a busy tone that no business wants. the wait time in the que is regulated by SLA’s the most famous one is “90% calls answered in X seconds”
In an outbound environment; you would want your predictive dialer to call more numbers out to filter our answering machines, busy signals, disconnects etc and kind of que up your customers for your CSRs here again the drop ratio should be minimum and in US it is regulated by FTC.
Hope this helps.