Technical information

Audio Interface
26 G24-L Module Hardware Description November 15, 2008
Audio Interface
The G24-L audio interface supports several audio devices and operating modes.
The audio interface's operating modes, active devices, amplification levels and speech processing
algorithms are fully controlled by the host application, through advanced programming options
and a versatile AT commands set.
The G24-L supports the following audio devices:
• Two single-ended and biased mono analog microphone inputs for use in a variety of modes.
• Two differential mono analog speaker outputs for use in a variety of modes.
• A digital serial interface using PCM coding.
Figure 2-14 shows the audio interface topology.
Figure 2-14: Audio Interface Topology
Handset Microphone Port
The handset microphone port is the G24-L power-up default active audio input for voice calls. It
is located on pin 61 at the G24-L interface connector, named MIC.
It is designed as a single-ended input and should be referenced to the G24-L analog ground.
The microphone input includes all the necessary circuitry to support a direct connection to an
external microphone device. It incorporates an internal bias voltage of 2.0V through a 2.0kΩ
resistor, and has an impedance of 1kΩ.