ITU-R M.494 PDF

General

class of emission J3E should be used; other classes of emission, e.g. H3E and R3E may be permitted, when necessary;

base and mobile stations should use the upper sideband;

the assigned frequency should be 1400 Hz higher than the carrier (reference) frequency;

for private mobile systems, the audio-frequency band should be 350-2700 Hz. For systems that can be connected to the public telephone network, the audio-frequency band may be increased to 300-3400 Hz.