Dictating machine is a machine which is used to take dictation from the higher authorities. It is used for transmitting oral messages and operates just like a audio tape recorder. There are two parts of a dictating machine namely Dictaphone and Ediphone. Notes are dictated to the Dictaphone through a mouthpiece and the uttered words are transcribed on a moving disc made of wax. The message so recorded is played back by the typist to help him to type the message 

Telefax : This is a device for transmitting drawings sketches diagrams from one place to . another. It transmits copies of important documents from one place to another at the speed of a telephone call. 

Public Address system : The system of communication is useful for calling staff and give information (or instructions). This system is usually installed in railway stations, airports, factories, offices etc. Under this system a loudspeaker is used to broadcast the appeal intended for the very noisy system and disturbs every employee.