The discharge current of cold-cathode gas-filled tubes has been effectively controlled by drawing a small lateral current from the discharge while maintaining a constant anode supply voltage. This mechanism, heretofore unreported, enables the glow discharge to be switched both on and off, producing a thyratron, a binary, switch, or a light indicator for computer use. It makes possible a new amplifier tube with current and voltage amplification obtainable in both the Townsend and glow regions of the discharge. Other devices employing this mechanism which have been demonstrated are a controlled frequency relaxation oscillator, a touch control switch, a time delay switch, and a detector of electrostatic charge and ac potential.