Abstract: A stimulator apparatus for applying a low frequency pulse train, modulating a high frequency pulse train, to a patient includes electrodes for placement on the patient in the area of stimulation. A programmable microprocessor generates the pulse train and an electrode driver, to which the low frequency pulse train is fed, is connected to the electrodes. An electrode monitor is connected to an output of the electrode driver, and the output of the monitor is fed to an interrupt terminal of the microprocessor whereby to detect an unacceptable electrode connection. The apparatus also includes a display console including a display arrangement and a switch group. The electrode driver, in accordance with the invention, provides an adjustable constant current to the electrodes.