The electrochemical interface is treated here as a multi-input/multi-output system. This approach allows application of new measurement techniques based on the sinusoidal perturbation or the sinusoidal response of nonelectrical quantities in addition to the usual electrochemical parameters (i.e., potential or current). Used in conjunction with the usual electro-chemical impedance, these new transfer functions allow extra information to be obtained on the interface. Some examples are given corresponding to input perturbation related. to light, magnetic field, temperature, and angular velocity of the electrode and output responses related to mass, optical reflection, and the currents in a ring-disk system.