Linksys SPA962, SPA942, SPA932, SPA922 manual Audio Configuration, For establishment of a secure call

SPA9x2 Phone Field Reference

Ext Tab

Parameter	Description
Mini Certificate	Base64 encoded of Mini-Certificate concatenated with
	the 1024-bit public key of the CA signing the MC of all
	subscribers in the group.
	Defaults to blank.
SRTP Private Key	Base64 encoded of the 512-bit private key per subscriber
	for establishment of a secure call.
	Defaults to blank.

Audio Configuration

A codec resource is considered as allocated if it has been included in the SDP codec list of an active call, even though it eventually may not be the one chosen for the connection. So, 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 G.729a resource is already allocated and since only one G.729a resource is allowed per device, no other low-bit-rate codec may be allocated for subsequent calls; the only choices are G711a and G711u. On the other hand, two G.723.1/G.726 resources are available per device.

Therefore it is important to disable the use of G.729a in order to guarantee the support of two simultaneous uses of the G.723/G.726 codecs.

Parameter	Description
Preferred Codec	Preferred codec for all calls. (The actual codec used in a call still
	depends on the outcome of the codec negotiation protocol.)
	Select one of the following: G711u, G711a, G726-16, G726-24,
	G726-32, G726-40, G729a, or G723.
	Defaults to G711u.
Use Pref Codec Only	To use only the preferred codec for all calls, select yes. (The call
	fails if the far end does not support this codec.) Otherwise,
	select no.
	Defaults to no.
Second Preferred Codec	The second preferred codec when the preferred codec cannot
	be used. If Use Pref Codec Only is enabled (set to yes), this
	parameter is not used.
	Defaults to Unspecified.
Third Preferred Codec	The third preferred codec when the preferred codec and
	second preferred codec cannot be used. If Use Pref Codec Only
	is enabled (set to yes), this parameter is not used.
	Defaults to Unspecified.

Linksys SPA9x2 Phone Administration Guide 173