Abstract: An improved pest repellent system which results in altering the existing electromagnetic field in the electricity supply of a building by inducing a phase shift in the supply by applying a voltage to a highly inductive coil or coils in a timed pattern which pattern is offensive to pests said system comprising providing: a device including a frame; at least one highly inductive coil appropriately wired within the frame and able to generate the altered electromagnetic field; a solid-state circuit for controlling supply voltage to the coil(s), a timing means of controlling the timed pattern; and optionally an earthing wire passing through the coil(s) to conduct said altered electromagnetic field to the environment around the device; wherein said timed pattern comprises a first period where the voltage is pulsed on and off through the coil(s) resulting in a phase shift in the alternating current of the supply and a second period of equal duration to the first period where supply of voltage to the coil(s) is pause