The title says "Text String Notation for Dial Sequences and
Global Switched Telephone Network (GSTN)".
Not clear about how this applies to sip. It sounds like pause/wait codes referenced here are for PSTN standards. However I remember Michigan Telephone mentioning something a looooong time ago that he used "w" or "p" as a pause. (How's that for remembering a useless detail! Don't ask me what I ate for breakfast though)
http://www.apps.ietf.org/rfc/rfc3601.html (Relevant section)
2.1 The "phone-string" definition
The text representation of the Dial Sequence elements is defined in the phone-string specification:
phone-string = 1*( DTMF / pause / tonewait / written-sep )
DTMF = ( DIGIT / "#" / "*" / "A" / "B" / "C" / "D" )
; special DTMF codes like "*", "#", "A", "B",
; "C", "D" are defined in [1].
; Important Note: these elements only apply for
; alphabetic strings used in DTMF operations.
; They are NOT applicable for the alphabetic
; characters that are mapped to digits on phone
; keypads in some countries.
pause = "p"
tonewait = "w"
written-sep = ( "-" / "." )
Note:
DTMF are the "DTMF elements", pause and tonewait are the "actions" and written-sep are the "separators".
The "pause" and "tonewait" elements interpretation of the phone- string depends on the specific devices and implementation using the specification. Thus their exact meaning is not mandated in this document. The next section provides some examples drawn from common practice. Both "pause" and "tonewait" are case insensitive.
Implementation of "pause" and "tonewait":
- one instance of a "pause" SHOULD be interpreted as a pause of
one second between the preceding and succeeding dial string
elements;
- a "tonewait" SHOULD be interpreted as a pause that will last
until the calling party hears a dial tone or another indication
that more dial string characters may be processed. An off-hook
indication MAY also be interpreted as this kind of indication
(meaning that the audio channel has been opened to the
receiving party);
- because these characters are not a part of the GSTN subscriber
address (telephone number) per se, any dial string characters
that succeed either a "pause" or "tonewait" SHOULD be sent
using DTMF signalling.
The use of written-sep elements is allowed in order to improve human readability of the phone-string. The written-sep are elements which can be placed between dial elements, such as digits etc. Any occurrences of written-sep elements in a phone-string MUST NOT result in any action. Conformant implementations MAY drop or insert written-sep into the phone-string they handle.
The phone-string definition is used in the following sections to explicitly describe the encoding of some specific subcases where it applies.