A
radiotelephone (or
radiophone) is a
communications system for transmission of speech over radio. Radiotelephone systems are not necessarily interconnected with the public "land line" telephone network. "Radiotelephony" means transmission of sound (
audio) by radio, in contrast to
radiotelegraphy (transmission of
telegraph signals) or
video transmission. Where a
two-way radio system is arranged for speaking and listening at a mobile station, and where it can be interconnected to the public switched telephone system, the system can provide mobile telephone service.