[VoiceOps] Help Identifying Strange Tone

[Jared Geiger]

I've heard that before when dialing a fax machine when sharing the primary
voice line, it would do that kind of behavior to make sure the caller was
actually a fax machine.

My guess is to save a voice caller's ears from getting the CNG tone whereas
a fax machine would detect the line as answered and would start to send the
tones causing the receiving fax machine to quit "ringing" and answer.

~Jared

On Wed, Jun 22, 2016 at 4:41 PM, David Knell <david.knell at telng.com> wrote:

> Best guess - it's fake ringback being generated by some auto fax/voice
> switch.
>
> --Dave
>
> On Wed, Jun 22, 2016 at 5:37 PM, Justin Grow <jgrow at flowroute.com> wrote:
>
>> This is an interesting one. I'm running into issues with a fax
>> application for a few numbers that are playing back a strange tone I have
>> yet to identify. I originally thought it was FAS with international
>> ringback, but it's occurring on a variety of numbers on various networks.
>> The tone is playing immediately upon answer. Any help identifying what is
>> causing this tone or what it is intended for is appreciated.
>>
>> The numbers are all fax lines and do get the proper CED after this tone.
>> I can't find any matching tone in the T.30 ITU-T rec. As best I can figure,
>> it's 400Hz with a 0.03s period on/off cycle, played 1s on 2s off. Listen at
>> the below link. Sorry for the compression; email me and I can send you the
>> original wav recording.
>>
>> https://clyp.it/vcq010th
>>
>>
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>>
>>
>
>
> --
>
> David Knell, Director, TelNG
> T: +44 1223 797979 / +1 970-315-4721
> W: http://www.telng.com
> H: http://www.daveknell.com
>
>
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