An instrument containing a transmitter for converting the acoustic signals of a person's voice to electrical signals, a receiver for reconverting electrical signals to acoustic signals, and associated signaling devices (the dial and alerter) for communicating with other persons using similar instruments connected to a network. The term “telephone” also refers to the complicated system of transmission paths and switching points, called the Public Switched Network (PSN), connected to this instrument. This article discusses only the instrument (also called a set); for a discussion of the telephone system .