Abstract: The switch has a gas discharge chamber, in which two electrodes, namely a cathode (11) and an anode (12), are contained, which are spaced a distance (d) apart and are separted from each order by an electrically insulating wall (9a) made of ceramic material or of glass. The cathode (11) is formed with a hole (5). The electrodes (11, 12) are joined to the insulating wall (9a) by a tight metal-ceramic joint or fused joint. The gas discharge chamber is filled with an ionizable low-pressure gas under such a pressure p that the product p.times.d has such a value that a gas discharge between the electrodes (11, 12) will be fired in response to a voltage applied thereof which is disposed in that branch of the firing voltage-pressure characteristic in which the firing voltage descreases as the pressure rises.