Section 2(7) in The Merchant shipping (Radio Direction Finders) Rules, 1968.
(7)in relation to classes of emission - "Class A-l" means telegraphy by on-off keying without the use of a modulating audio frequency "Class A-2" means telegraphy by the on-off keying of an amplitude-modulating audio frequency e audio frequencies, or by "the on-off keying of the modulated emission;"Class B" means damped waves;
