A driver unit comprises a latch circuit for holding digital image data in a voltage state, a digital-to-analog converter, and a voltage compensator circuit for raising the analog display voltage. In one embodiment, at each descheduling event of the thread following an execution interval, an effective CPU time is determined. One of the plurality is designated a primary tunnel configured to accept packets. Superimposition of the first treatment zone and the one or more additional treatment zones defines a non-continuous circumferential treatment zone without formation of a continuous circumferential lesion. The access receiving port can have the same design or different designs.