IEC 60244-4:1973

Applies to all transmitters for A3 class of operation. Applies also to radiotelephony transmitters with 1, 2, 3 or 4 channels for A3A, A3B, A3H and A3J class of operation, and to frequency modulated transmitters for monophonic sound broadcasting. Applies in part to transmitters for A7A and A7B class of operation.
IEC 60244-4 itself describes standard operating conditions, standard modulation input arrangements and frequencies (Section One). It also describes standard methods to be used for measuring input impedance, the amplitude/frequency characteristics and the intelligible crosstalk (Section Two).