Abstract: An interface apparatus, for remotely controlling a plurality of solenoid actuated switching relays having first and second energizing coils, is capable of providing momentary first and second electrical signals respectively in response to an interruption of an input signal to the apparatus and the initiation of the input signal. The interface apparatus includes a first comparator sensing a change in the input signal, a second comparator sensing a change in the output of the first comparator so as to maintain the second comparator output 180 degrees out of phase with the first comparator output, and first and second monostable multivibrators that each have a trigger input connected to the output of a corresponding comparator so as to generate a momentary electrical signal when the trigger input senses a negative excursion in a change of state at the output of the corresponding comparator.