Linksys SPA942, SPA962 manual G729a Enable, Yes. Otherwise, select no, G723 Enable, G726-16 Enable

SPA9x2 Phone Field Reference

Ext Tab

Parameter	Description
G729a Enable	To enable the use of the G.729a codec at 8 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
G723 Enable	To enable the use of the G.723a codec at 6.3 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
G726-16 Enable	To enable the use of the G.726 codec at 16 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
G726-24 Enable	To enable the use of the G.726 codec at 24 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
G726-32 Enable	To enable the use of the G.726 codec at 32 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
G726-40 Enable	To enable the use of the G.726 codec at 40 kbps, select
	yes. Otherwise, select no.
	Defaults to yes.
Silence Supp Enable	To enable silence suppression so that silent audio frames are
	not transmitted, select yes. Otherwise, select no.
	Defaults to no.
DTMF Tx Method	Select the method to transmit DTMF signals to the far
	end: InBand, AVT, INFO, Auto, InBand+INFO, or
	AVT+INFO. InBand sends DTMF using the audio path.
	AVT sends DTMF as AVT events. INFO uses the SIP INFO
	method. Auto uses InBand or AVT based on the outcome
	of codec negotiation.
	Defaults to Auto.

A codec resource is considered allocated if it has been included in the SDP codec list of an active call, even though it eventually might not be chosen for the connection. If the G.729a codec is enabled and included in the codec list, that resource is tied up until the end of the call whether or not the call actually uses G.729a. If the G729a resource is already allocated (and since only one G.729a resource is allowed per SPA), no other low-bit-rate codec can be allocated for subsequent calls. The only choices are G711a and G711u.

Linksys SPA9x2 Phone Administration Guide 174