scope:

This recommendation applies to multi-electrodes tubes and valves, with the exception of cathode-ray tubes. It describes the system used for numbering the electrodes of the same type in multi-electrode tubes and valves and for assigning designations to the units of multiple-unit tubes and valves. For tubes and valves made with two or more similar units, the numbering of the units is given as derived from the basing arrangement. This recommendation shall not be used to determine the basing arrangement of any type. The designations determined from this recommendation shall also apply to other tube or valve elements, such as heaters, shields etc.