H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
H03K17/52—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of gas-filled tubes