> 6.4.1 | Configuration of the Internal Microphone Supply

> The microphone power supply voltage (VMIC) is programmable via the command:
> AT^SNFM=[<MicSwitch>],MicVccCtl>]
> This gives you greater flexibility in connecting audio accessories or using the microphone interfaces for a variety of functions other than audio.
> The parameter <MicSwitch> mutes or activates the microphone at the currently selected audio interface. The parameter can only be set when there is an active call.
> The parameter <MicVccCtl> controls the power supply voltage VMIC. Note that the first parameter <MicSwitch> must be omitted when setting <MicVccCtl>.
> AT^SNFM=,0: Permanently switches off the power supply at VMIC.
> AT^SNFM=,1: Permanently switches on the power supply at VMIC.
> AT^SNFM=,2: Default setting. Power at VMIC is applied only during a call.
> This means that with AT^SNFM=,0 or AT^SNFM=,1 the power supply can be controlled independently of GSM activity. The permanent power supply can be used to feed an audio application even when the GSM part is inactive, for example if the host device integrates a dictaphone or voice recorder connected in parallel to MICP1 and MICN1 respective MICP2 and MICN2.