Abstract: 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.