Using both SNR and TCF modem metrics, quick diagnostics of poor or failing receiver performance can be made. The following table shows how these two parameters can be used:
|
Indication |
SNR |
Training zeros |
Possible NFX receiver performance |
|---|---|---|---|
|
Good line quality |
>25 dB |
> 1.35 seconds |
No problems encountered. |
|
Good line quality Non-compliant TCF |
>25 dB |
1.0 to 1.35 seconds |
Possible FTT due to non-compliant sending fax. Possible line errors in non-ECM mode, and retransmits in ECM mode. |
|
Marginal line quality Compliant TCF |
22 to 25 dB |
1.0 to 1.35 seconds |
Possible FTT due to line conditions. Possible line errors in non-ECM mode, and retransmits in ECM mode. |
|
Poor line quality Compliant TCF |
<22 dB |
< 1.0 seconds |
Probable FTT due to poor line conditions. Possible line errors in non-ECM mode, and retransmits in ECM mode. |