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.