| abstract |
Method and apparatus for alternately providing positive and negative direct current voltages to a single twisted pair includes a power source configured to provide a first signal and a second signal, the first and second signals having different polarities, a controller configured to provide a control signal in accordance with a predetermined timing signal, and a voltage alternating switch circuit having first and second output terminals, the voltage alternating switch circuit coupled to the power source configured to receive the first and second signals, the voltage alternating switch circuit further coupled to the controller configured to receive the control signal, and in accordance thereto, providing first and second signals alternately to first and second output terminals, such that the adverse corrosive effect of positive voltage line powering is minimized. |