The device consists of the speech and the dialer functions. It provides the DC line interface circuit that terminates the telephone line, analog amplifier for speech transmission and necessary signals for either DTMF and pulse dialing. When mated with a tone ringer, a complete telephonecan be producedwith just two ICs. TheDClineinterfacecircuit developsits ownlinevoltage acrossthedeviceandit is adjustableby externalresistor to suit different country's specification. A built-in LED driver can deliver excess line current to external LED indicator(s) during dialing and speech mode. The LED(s) can be used either for keyboard illumination purpose or for tone mode indication during softswitch and mixed mode dialing by connecting MU/MFI pin to VDDandGND oranyrowrespectively.The LEDcurrent is limited to 17mA (typical).