Polycom SIP 3.1 manual Chord-Sets chord, There are three blocks of chord sets

			Configuration Files
	Permitted
Attribute	Values	Default	Interpretation
tone.dtmf.viaRtp	0, 1	1	If set to 1, encode DTMF in the active
			RTP stream, otherwise, DTMF may be
			encoded within the signaling protocol only
			when the protocol offers the option.
			Note: tone.dtmf.chassis.masking should
			be enabled when tone.dtmf.viaRtp is
			disabled.
tone.dtmf.rfc2833Control	0, 1	1	If set to 1, the phone will indicate a
			preference for encoding DTMF through
			RFC 2833 format in its Session
			Description Protocol (SDP) offers by
			showing support for the phone-event
			payload type; this does not affect SDP
			answers, these will always honor the
			DTMF format present in the offer since
			the phone has native support for RFC
			2833.
tone.dtmf.rfc2833Payload	96-127	101	The phone-event payload encoding in the
			dynamic range to be used in SDP offers.

Chord-Sets <chord/>

Chord-sets are the building blocks of sound effects that use synthesized rather than sampled audio (most call progress and ringer sound effects). A chord-set is a multi-frequency note with an optional on/off cadence. A chord-set can contain up to four frequency components generated simultaneously, each with its own level.

There are three blocks of chord sets:

•callProg (used for call progress sound effect patterns)

•ringer

•misc (miscellaneous)

All three blocks use the same chord set specification format.

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