Bell MF tone receiver

What does it do?

The Bell MF tone receiver module provides for the detection of the repertoire of 15 dual tones needs for various Bell MF signalling protocols. It is compliant with ITU-T Q.320, ITU-T Q.322, ITU-T Q.323B.

How does it work?

Basic Bell MF tone detection specs:

Note: Above -3dBm the signal starts to clip. We can detect with a little clipping, but not up to 0dBm, which the above spec seems to require. There isn't a lot we can do about that. Is the spec. incorrectly worded about the dBm0 reference point, or have I misunderstood it?

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