Subject: [AVT] Re: Question on MFR1 in draft-ietf-avt-rfc2833bis-02.txt

From: Henning Schulzrinne <[email-masked]>
Date: Sun, 29 Jun 2003 13:09:03 -0400

Zhenfu Lin wrote:

> Hello editors.
> 
> I have a couple of quesions regard MFR1.

My apologies for the delay in responding.

> 
> 1) What is the frequency pair for MF R1 S3 in Table 6 of 
> draft-ietf-avt-rfc2833bis-02.txt? (I am guessing that it is frequency
> pair 700/1700 Hz.)

This was a mistake, related to the item below.

> 2) Both KP and KP1 refer to the same frequency pair, namely 1100/1700
> Hz. In Table 6, KP is mapped to 138 and KP1 is mapped to 139. So,
> frequency pair 1100/1700 Hz maps to two codes (138 and 139). - a:
> Does this mean that one of these codes is used when a RFC 2833 packet
>  is generated? Which one should be used? - b: Does this mean that the
> receiver is prepared to receive both codes, and map both to the
> frequency pair 1100/1700 Hz?

This was a bug caused by confusion in the description and labeling of 
these tones. I've now cleaned this up and removed duplicates, so that 
each frequency pair has a single label:

MF 0\ldots 9                                & 128\ldots 137 & & yes\\
MF 700/1700  (Code 11, KP3P, ST3P)          & 138           & & yes\\
MF 1100/1700 (KP, KP1)                      & 139           & & yes\\
MF 1300/1700 (KP2, ST2P)                    & 140           & & yes\\
MF 1500/1700 (ST)                           & 141           & & yes\\
MF 900/1700 (Code 12, STP)                  & 142           & & yes\\

I've looked at a variety of sources (ITU Q.140/Q.151, Freeman, GR-506) 
and the labeling seems now self-consistent.

-03 should appear early next week.

> Thank you.
> Zhenfu

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