Abstract: A variable impedance circuit for use in an external circuit. The impedance value may be altered by an external circuit. The invention consists of a plurality of two terminal impedance elements connected in series. A node is provided between each pair of impedance elements in the series chain. At least one of the first element and last elements in the series chain are connected to terminals which are accessible for connection to the external circuit. Each of the nodes may be connected to a terminal which is also accessible for connection to the external circuit. An electrically reprogrammable read-only memory stores the identity of the node connected such that the identity of this node is retained when power is removed from the invention. When power is returned to the invention, the node which was previously connected to the terminal is automatically reconnected.