by the use, as active elements, of gas-filled tubes

Full Title

Electronic switching or gating, i.e. not by contact-making and –breaking (gated amplifiers H03F3/72; switching arrangements for exchange systems using static devices H04Q3/52) > characterised by the components used (H03K17/04 - H03K17/30, H03K17/94 take precedence) > by the use, as active elements, of gas-filled tubes