A stimulator for causing involuntary mandibular closure. In a "test" mode a constant voltage is applied to left and right electrode circuits, and the currents through the electrode circuits are measured to determine electrode circuit conductivity. A first comparator circuit flashes respective "open" circuit warning lamps if the current through either of the electrodes is less than a preset value, and it flashes a "good" connection indicator lamp if the current through both electrodes is greater than the preset value. A second comparator circuit determines if the current through one electrode exceeds the current through the other electrode by a preset value, and flashes respective "low" current warning lamps in response thereto. In the "pulse" mode an oscillator repetatively charges a capacitor to a high voltage through a pulse transformer, and the high voltage is then gated to a control circuit which generates a current pulse having an adjustable amplitude through the electrode circuits to produce involuntary mandibular closure. The amplitude of the current through one electrode circuit with respect to the current through the other electrode circuit may be adjusted with a balance control. In the "pulse" mode, the battery voltage is also measured, and respective lamps flash in synchronism with the current pulses to indicate whether the battery is producing the proper voltage or whether the battery must be replaced.