An adaptive power supply span powers devices used in telecommunications. It includes a power circuit and control circuit that receives power and sense signals therefrom and provides a control signal thereto and distinguishes between a first network interface load having a constant voltage input power requirement and a second network interface unit load having a constant current input power requirement. A voltage control circuit and current control circuit are interconnected together and connected to the power circuit. A control signal from the voltage control circuit and current control circuit extends to the power circuit. The control circuit maintains a fixed output voltage for constant voltage regulation for the first network interface unit load, if the output current remains below a threshold current. The circuit limits the output current to a regulated value for constant current regulation below the initial maximum value for powering a second network interface unit if the initial output current is greater than the threshold current for a time greater than a threshold time.