Subject: [AVT] rfc2833: DTMF volume

From: "Prabhu, Raghavendra" <[email-masked]>
Date: Mon, 4 Nov 2002 14:55:20 -0800

Hi folks

There is some text in rfc2833 describing volume of DTMF (event payload
format):
"The range of valid DTMF is from 0 to -36 dBm0 (must accept); lower than -55
dBm0 must be rejected (TR- TSY-000181, ITU-T Q.24A)."

I am looking at Q.24AnnexA and I am failing to locate any requirement that
says that the DTMF receiver must accept 0 to-36dBm0. Q.24 says must accept
upto -25dBm (AT&T). Q.24 does say, must reject anything lower than -55dBm.

I would assume that RFC2833 is not a DTMF receiver spec. So where does "must
accept -36dBm0" come from? 

Thanks
Raghavendra

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Audio/Video Transport Working Group
[email-masked]
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From: Henning Schulzrinne <[email-masked]>
Date: Tue, 05 Nov 2002 22:40:01 -0500

> dBm0 must be rejected (TR- TSY-000181, ITU-T Q.24A)."

I currently don't have access to TR-TSY-00181. The only other reference 
I have is ETSI TS 101 235-4 V1.1.1 (2000-05), which only mentions

"The level of each of these two signalling frequencies is within the 
range -43 dBV to -5 dBV"

-43dbV is somewhere around -41 dBm0, if I'm not mistaken.

Anybody have some real data?