FXO coefficients file types:

1) MP1xx12-1-12khz-fxo.dat - relevant for any MP1XX, supporting detection of 12 KHz metering tone.
2) MP1xx12-1-16khz-fxo.dat - relevant for any MP1XX, supporting detection of 16 KHz metering tone.
3) MP1xx10-2-16khz-TBR21-fxo.dat - relevant for any MP1XX , supporting detection of 16 KHz metering tone, comply with TBR21 standard (Pan European).
4) MP1xx10-4-16khz-fxo-low-frq-ring.dat - relevant for any MP1XX, supporting detection of 16 KHz metering tone, enable detection of low ring frequencies (under 20Hz).

* If metering tone type (16Khz or 12 KHz) is not important, it is recommended to use coefficients file number 2.
