The present invention improves control of currents in a multi-site direct current neurostimulation system. Precise control incorporates three constant current sources in a system consisting of spinal, polarizing and peripheral circuits. Constant current sources (sinks) are placed on the high side of the peripheral circuit and one sink in series on the low side of the spinal circuit in a four electrode configuration, for maintaining both predetermined currents, and current ratios, as the electrode/skin impedance and body impedance vary over the course of a treatment. Resistive steering is also implemented.
