The telephone circuit U4089B-P is a linear integrated circuit for use in feature phones, answering machines and fax machines. It contains the speech circuit, sidetone equivalent and ear protection rectifiers. The circuit is line-powered and contains all components necessary for the amplification of signals and adaptation to the line. An integrated voice switch with loudspeaker amplifier enables loudhearing or handsfree operation. With an anti-feedback function, acoustical feedback during loudhearing can be reduced significantly. The generated supply voltage is suitable for a wide range of peripheral circuits.