To protect an electrical load connected to an output port from anomalous electricity in an apparatus that provides output electricity at the output port from input electricity accepted through an input port thereof, an input sensing unit is electrically connected to the input port and configured to indicate an overvoltage event. A power control unit generates, responsive to the overvoltage event, a modulation signal that defines at least one amplitude notch of variable temporal width. A switching mechanism electrically interposed between the input port and the output port transitions into conducting and non-conducting states in accordance with the modulation signal to superimpose the amplitude notch on electricity conveyed to the output port through the switching mechanism.