​Specifies dimensions for the insulator coupling devices used with insulators of ceramic material or glass for use on a.c. overhead power and traction lines with a nominal voltage greater than 1000 V and frequency not greater than 100 Hz. It applies to insulator units, strings and sets, pin insulators, and to line post insulators and shackle insulators of similar design when used in sub-stations. Locking devices are also covered.