Transcutaneous electrical nerve stimulator

Claim 1

A portable transcutaneous electrical nerve stimulator adapted to apply electrical stimulating pulses to the body of a patient by way of body contacting surface electrodes, comprising in combination: (a) a source of direct current potential having first and second terminals; (b) oscillator means including (1) a unijunction transistor having first and second base electrodes respectively coupled to said first and second terminals of said source of direct current potential and an emitter electrode, (2) a timing circuit including first and second variable resistors and a capacitor connected between said first and second variable resistors, said timing circuit connected in series between said first and second terminals of said source of direct current potential, and (3) means connecting said emitter electrode of said unijunction transistor to the connection between said first variable resistor and said capacitor; (c) semiconductor amplifier means including (1) first and second transistors, each having an emitter electrode, a collector electrode and a base electrode, the base electrode of said second transistor being connected to the emitter electrode of said first transistor and the emitter electrode of said second transistor being coupled to said first terminal of said source of direct current potential, (2) a light emitting diode coupled between said collector electrode of said first transistor and said second terminal of said source of direct current potential, and (3) means coupling the base electrode of said first transistor to said second base electrode of said unijunction transistor; and (d) output means including, (1) a pulse transformer having a primary winding and at least one secondary winding, (2) means connecting said primary winding of said pulse transformer between said collector electrode of said second transistor and said second terminal of said source of direct current potential, (3) jack means adapted to be connected to said surface electrodes, and (4) a variable voltage divider coupled between said secondary winding of said pulse transformer and said jack means, the arrangement being such that biphasic, asymmetrical pulses of adjustable frequency, pulse width and pulse amplitude may be applied to the body of the patient, said frequency being determined by said first variable resistor, said pulse width being determined by said second variable resistor and said pulse amplitude being determined by said variable voltage divider.