Fax Answer Tone Question

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

ITU communication standards V.27 V.29 V.17V.34 V.34bis

You can fin the specs here

from V.34...

10.1.2.1A Tone A is a 2400 Hz tone transmitted by the answer modem. Transitions between A and A, and similarly between A and A, are 180 degree phase reversals in the 2400 Hz tone. During the transmission of A and A, the answer modem sends a 1800 Hz guard tone without any phase reversals. Tone A is transmitted at 1 dB below the nominal transmit power while the guard tone is transmitted at the nominal transmit power. NOTE ? The bandwidth of a tone with phase reversals should not be constrained in a way that appreciably affects the accuracy of round trip delay measurements. 10.1.2.2B Tone B is a 1200 Hz tone transmitted by the call modem. Transitions between B and B, and similarly between B and B, are 180 degree phase reversals in the 1200 Hz tone. NOTE ? The bandwidth of a tone with phase reversals should not be constrained in a way that appreciably affects the accuracy of round trip delay measurements.

Cheers

Thanks, Martin! So the "click"/strobing I'm hearing is actually a phase reversal? ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I think so, if you read into the v.34 document they explain the answer negotiation. TONE A and TONE B are defined early on in the document.

Cheers

I do not know about the standards, but that "strobe" is from the fact that a FAX machine identifies itself on pickup.

Well, if one uses a telephone to call a FAX, there cannot be any negotiation, yet one hears that (what i call) "tweedle".