A phone system is made up of several telephones that are linked together to provide advanced telephony features such as call handling and transferring, conference calling, call metering and accounting, private and shared voice message boxes, and so on. The telephone instrument, as it has been since its inception, is comprised of the following functional components: a power source, a switch hook, a dialer, a ringer, a transmitter, a receiver, and an anti-sidetone circuit. These aspects are discus