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ATA192 1st Call Waiting Tone Sounds Like a Fax, 2nd sounds fine

George Spanos

I am functionally testing a Cisco ATA192 on firmware (11-1-0MPP0401-002 Oct 18 2020) and the 1st call waiting tone sounds like a staic-fax tone mixed with the phones regular ringtone and then the second CW tone sounds normal. I noticed that the CW1 cadence is different than the CW2 etc.. so I changed CW1 to "30(.1/.1, .1/9.7)" to match CW2 tone but that made no difference. Any suggestions? Voice->Regional settings attached and video of the interesting tone...

1 Reply 1

Dan Lukes

Call Waiting is the signal that's delivered during actual call to inform user there's another call waiting. There are various method how to deliver such signal thru POTS line. To work correctly, the format used by exchange device (ATA192 here) must be supported by particular phone connected.

Based on the sound you disclosed I assume the ATA192 is configured to use polarity reversal (two clicks) followed by DTAS followed by Type II caller ID digital info (it sounds like Bellcore FSK or ETSI FSK kind, but consider it blind shot, I can't reliably identify digital format by naked ear). Compatible phone should mute them and take appropriate action based on data received. Your phone seems to recognize neither polarity reversal nor DTAS as special signal, thus it do nothing and you hear digital transmission as is.


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