> 3.15 | Audio Interfaces

> TC65 comprises three audio interfaces available on the board-to-board connector:

> • | Two analog audio interfaces.

> • | Serial digital audio interface (DAI) designed for PCM (Pulse Code Modulation).

> This means you can connect up to three different audio devices, although only one interface can be operated at a time. Using the AT^SAIC command you can easily switch back and forth.
> Figure 24: Audio block diagram
> To suit different types of accessories the audio interfaces can be configured for different audio modes via the AT^SNFS command. The electrical characteristics of the voiceband part vary with the audio mode. For example, sending and receiving amplification, sidetone paths, noise suppression etc. depend on the selected mode and can be altered with AT commands (except for mode 1).
> Both analog audio interfaces can be used to connect headsets with microphones or speakerphones. Headsets can be operated in audio mode 3, speakerphones in audio mode 2. Audio mode 5 can be used for direct access to the speech coder without signal pre or post processing.
> When shipped from factory, all audio parameters of TC65 are set to interface 1 and audio mode 1. This is the default configuration optimized for the Votronic HH-SI-30.3/V1.1/0 handset and used for type approving the Siemens reference configuration. Audio mode 1 has fix parameters which cannot be modified. To adjust the settings of the Votronic handset simply change to another audio mode.