After the Introduction, which deals briefly with the speed limitations of the present type of cold-cathode gas-tube counter, the mechanism which produces a reduction in the breakdown voltage of a gap adjacent to a discharging gap is outlined and typical curves are given demonstrating the relationship between this reduction in breakdown voltage and other important parameters. A simple type of multi-cathode tube is described, together with a first development, which has led to the G10/240E, a multi-electrode decade counter capable of operating at speeds up to 20 kc/s. Important design features of this multi-electrode tube are treated in detail, and a method of computing the d.c. tolerance range of this type of tube is given. After a discussion of the derivation of important limits on the driving pulse and other circuit parameters, typical performance figures are quoted, and reference is made to the exhaustive type of automatic testing to which each tube is subjected in production. In conclusion, a few very general remarks are made concerning the way in which the tube may be used.