The mechanical devices used for oral communication are:
(b) Loudspeaker System
(c) Recorded message
(d) Dictating machine,
(a) Telephone – Telephone is a mechanical device meant to reproduce sound at a distance through the help of cables or wires. It is a convenient and quickest method of communication.
(b) Loudspeaker System — It is a traditional mechanical device and is a type of public address system. These are used in railway stations, bus stands and airports to call persons or give instructions.
(c) Radiophone — It is a device where instruments are not connected with wire but facilitate oral communication. This is otherwise called as wireless system.
The other facilities of oral communication are through recorded message in cassettes and magnetized discs or tapes and through a dictating machine.