This European Standard is intended to give general minimum frame requirements for units that are independent of the technology used for switching and/or monitoring of individual or group of lamps in an AGL series circuit. This European Standard - applies to the units that are directly electrically connected to the primary or secondary side of an AGL series circuit and are needed to provide the selective switching and/or monitoring of lamps, - does not cover communication protocols and application procedures, - does not treat system aspects that influence the AGL operation. NOTE: These units may be used forming part of either a SMGCS or A-SMGCS to guide and/or control the surface movement of aircraft by means of visual aids.