MFC-8500 fax operation

You could try to listen for noise/crackles on lin itself, in australia we have a system for checking lines called folds (fax omline diag service) I guess all phone providers have one, contact carrier to see if your have same, all it is is a number we send a fax to and telecom send a report back instantly telling us line condition then we set fax attenuation accourdingly to eliminate problems that are simular to yours. Faxs start transmittion at 36000 bits per sec but step down to as low as 4800 BPS if line quality is poor You could try to listen for noise/crackles on lin itself, in australia we have a system for checking lines called folds (fax omline diag service) I guess all phone providers have one, contact carrier to see if your have same, all it is is a number we send a fax to and telecom send a report back instantly telling us line condition then we set fax attenuation accourdingly to eliminate problems that are simular to yours. Faxs start transmittion at 36000 bits per sec but step down to as low as 4800 BPS if line quality is poor