This attribute specifies the voice law to be established for the IWF
to Public Switched Telephone Network (PSTN) modem link for
calls established by this GsmIwfCallServer. Valid values are:
aLaw, a protocol for encoding voice-band audio, Pulse Code
Modulation (PCM).
muLaw, a protocol for encoding voice-band audio, PCM.
Note that this value must match the voice law used at the Mobile
Services-switching Center (MSC) connected to this
GsmIwfCallServer.