G.165 Modem Tone Detect / Tone Disable

G.165 Modem Tone Detect / Tone Disable

In telecommunications systems, it is often necessary to detect the presence of a voice-band modem signal. In particular, when using a line echo canceller, it is desirable to disable certain aspects of echo cancellers or echo suppressors. Modems therefore precede their transmissions with a disable tone. These tones are described in ITU recommendations G.164 and G.165.

Disabling Echo Cancellers (ITU-T G.165 / G.168): Echo cancellers are vital for clear human voice conversations but they distort data transmissions. When an ITU detector catches the 2100 Hz phase-reversed ANS/ANSam tone, it instantly disables the echo cancellers on that circuit so data can pass through cleanly.

Adaptive Digital’s G.165 Tone Detector detects both of the aforementioned disable tones.