ISO 7376:2009 gives general requirements for laryngoscopes used for intubation, and specifies critical dimensions for the handle and lamp of hook-on type laryngoscopes. It also addresses the interchangeability of blades and handles. It is applicable only to instruments with an internal battery-operated power source for illuminating the larynx, since electrical safety requirements can be more stringent for instruments connected to mains or external power packs. It is not applicable to surgical instruments known by the same generic name, nor is it applicable to flexible laryngoscopes or laryngoscopes designed for surgery, laryngoscopes powered from mains electricity supply, laryngoscopes connected by light-transmitting cables to external light sources, or video laryngoscopes designed to work with an external video system.