Patent ID: 6731748
Filing Date: 2004-05-04
Classification: H04M

Abstract:
An audio interface for a wireless communications system, comprising:a radio antenna unit (RAU), for receiving and transmitting radio signals, having an audio codec coupled thereto at a first location; a plurality of deskset phones disposed at one or more second locations, each desket phone being coupled by cable to said audio codec and including a microphone for generating said transmit signal from an acoustic input generated at the first location; a transmit path comprising: a dedicated transmit cable for carrying a transmit signal from said deskset phones to said audio codec, a bias circuit coupled to the output of said microphone for providing the microphone with a floating ground and causing said transmit signal to be a differential audio signal, and for converting single mode power supply noise to common mode noise which is added to said transmit signal, an amplifier configured with a differential input and a differential output, coupled to the output of said bias circuit and the input of said dedicated transmit cable for amplifying said transmit signal and for rejecting said common mode noise, and a transformer coupled to the output of said dedicated transmit cable for rejecting common mode noise generated by said cable, and for passing said transmit signal to the audio codec; and a receive path comprising a dedicated receive cable electrically isolated from said dedicated transmit cable for carrying a receive signal from said audio codec to said deskset phones.