This specification covers portable marker lights for general emergency use and on ground obstructions, airfield runways and taxiways, and landing areas for rotary wing aircraft.
Marker lights shall be of the following types, as specified (see 6.3):

   Type I       - Dry  battery  operated,                     precision optical sys-                     tem.     Type II      - Mercury battery  oper-                    ated, precision optic-                    al system.     Type IIIA    - Dry  battery  operated,                     nonprecision   optical                     system,  two-position                     switch.     Type IIIB    - Dry  battery  operated,                     nonprecision   optical                     system, three-position                     switch, flash capabil-                     ity.    Type IV      - Dry  battery  operated,                     precision optical sys-                     tem, flashing red light.

Intended Use: The lights covered by this specification are intended for use as emergency marker lights for applications requiring portability and short range visibility from the air, such as marking closed runways, helicopter operations, soft spots, or runway lighting on aircraft landing strips.