MIL-DTL-25971C, DETAIL SPECIFICATION: LIGHT, AIRPORT TRAFFIC CONTROL, SDU-4/U (07-JAN-2009) [SUPERSEDING MIL-L-25971B]

MIL-DTL-25971C, DETAIL SPECIFICATION: LIGHT, AIRPORT TRAFFIC CONTROL, SDU-4/U (07-JAN-2009) [SUPERSEDING MIL-L-25971B]., This specification covers one type of airport traffic control light designated SDU-4/U. The lights are intended to be used in permanent or mobile air-traffic control towers to control air traffic in the event radio transmission is not available.