A plurality of inductors are connected in series between a load resistor and a first transistor, and a plurality of second transistors provided in parallel are connected to the plurality of inductors. Based on the records submitted by the customers, the dialing mode of the hosted software system initiates calls to the contacts, and when and if a right-party contact is reached for a particular customer, the call is delivered from the dialing mode to an agent at one of a plurality of call centers of the particular customer according to predefined agent selection rules for outbound call routing. Thus a voltage difference of the sampled sensing signal and the reset signal remains unchanged, and their levels may fall within a linear input range by adjusting their levels.