Error 345 a communication error occured when ending a Fax .what is this and why does it happen?

I changed the fax resolution from "fine" to "standard" using the button on the keyboard.
After this, the page who was not faxable have been transmitted without problem.
Paolo

Error Code: 344, 345, 346, 347, 348, 349 ECM, 350 ECM, 351 ECM, 352 ECM, 353 ECM, 354, 355 Definitions

• The remote machine failed to respond to a fax command from the local machine because the connection was interrupted. These errors can occur if the phone lines in the area to be faxed are old or there is noise (static on the phone line). Other reasons can include power outages and other power-related problems.
• The call-waiting service can cause this error. The click, heard for an incoming call, is actually a momentary disconnect of the line.
• The remote user pressed the Stop key while the reception was in progress.
• Under rare conditions, incompatibility between the two machines might cause the remote machine to abandon the call.

• Retryt the fax reception at a different time when telephone line conditions have improved. Call the telephone provider if line conditions fail to improve.
• Disable ECM. Errors might still occur, and might result in a degraded image quality on the received page. However, the ability to send the entire document will be improved. Click here for instructions on enabling and disabling ECM (c00060802) (in English).
• Try sending at a lower transmission speed.