Which of the following is an acceptable bandwidth for digital voice or slow-scan TV transmissions made on the HF amateur bands?

توضیح

Slow-scan television is an image emission, and on HF a non-phone emission may not exceed the bandwidth of a communications quality phone emission of the same modulation type, conventionally about 3 kHz. A digital voice signal carrying a phone emission designator counts as phone rather than non-phone, so its limit comes instead from the general rule that no transmission may occupy more bandwidth than necessary for the information rate and emission type. Neither rule states a number, and 3 kHz is the only choice consistent with HF phone practice; the wider figures describe VHF and higher bands.