A new three‐electrode glass switch device is described that shows performance like a thyrister. The planar electrodes are obtained by dividing a chromium layer by two perpendicular gaps in four parts. Two of these parts are connected and form the common electrode. The two remaining parts are used as control electrode and load electrode. The device is in the on state, if the load electrode is connected by a conducting filament to the common electrode. Investigations of the performance of the new device show that the load diode can be triggered by a voltage pulse supplied to the control electrode if the control diode is in the off state. It can also be triggered by a current pulse supplied to the control electrode, if the control diode is in the on state and operated by a dc current. The measured performance of the new device is explained under the assumption that in both diodes a thermal‐switching mechanism takes place.