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Linksys IP Phone Administrator Guide
Firmware Version 5.1
Chapter 5 Linksys IP Phone Field Reference
Ext Tab
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.
Since two G.723.1/G.726 resources are available per SPA, you should disable the use of G.729a to
guarantee support for two simultaneous G.723/G.726 codecs.
FAX CNG Detect Enable Defaults to yes.
FAX Passthru Codec Codec to use for FAX passthru (G711u or G711a).
Defaults to G711u.
FAX Codec Symmetric Force unit to use symmetric codec druing FAX passthru.
Defaults to yes.
FAX Passthru Method Choose None, NSE, or ReINVITE.
Defaults to NSE.
FAX Process NSE Defaults to yes.
FAX Disable ECAN Set to yes to automatically disable Echo Canceller when FAX tone is detected.
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.
Hook Flash Tx Method Select the method to signal Hook Flash events:
• None: do not signal hook flash events
• AVT: use RFC2833 AVT (event=16)
• INFO: use SIP INFO method with the signal line “signal = hf” in the message body. The
MIME type for this message body is taken from the <Hook Flash MIME Type> parame-
ter.
Defaults to None.
Symmetric RTP Enable symmetric RTP operation. If enabled, the SPA sends RTP packets to the source
address of the last received valid inbound RTP packet. If disabled, the SPA sends RTP to
the destination as indicated in the inbound SDP.
Defaults to yes.
Release Unused Codec This feature allows the release of codecs not used after codec negotiation on the first call,
so that other codecs can be used for the second line. To use this feature, select yes.
Otherwise, select no.
Defaults to yes.
Field Description