Fax Machine ECM mode

Can you tell me more about ECM mode?

In the past, I have written that one of the steps to successfully faxing over VoIP is to turn off ECM, or Error Correction Mode, on your fax machines. When ECM is enabled, it finds and solves the errors that may occur in the transmission process, which are generally a result of the noise on the telephone line. Most fax machines have ECM, and many sources will tell you that turning off this feature will give you a better chance of success when faxing without a traditional dial tone.

Well, reader “JM” has a different take on the situation, and took the time to email in and tell me about it. JM tells me that he’s worked plenty with fax over VoIP, and found that having the ECM turned off isn’t necessary. In fact, he says that disabling ECM is more trouble than it’s worth. “It might increase your success rate,” he says. “But pages may be missing, cut in the middle, or unreadable.”

Further, JM believes that changing the baud rate on a machine from 14400 to 9600 bps or lower is also a mistake. “The reason is that 14400 is later, and includes forward error correction (in addtion to ECM mode),” explains JM. “9600 doesn’t have anything. You might get a slight gain in the lower baud rate, but you lose that gain due to having no error correction at all.”

In a related technical issue, I recently gave advice to a person who was receiving blank faxes from one particular number . While I offered several solutions to this issue, JM believes this is yet another example of what happens when either the recipient or the sender turns off ECM code. So, if you are experiencing that issue, or anything similar to unreadable fax pages, check your ECM setting. And remember to ask your fax correspondents to do the same, since the process will work best if everyone has it turned on. You might find that JM is correct, and that turning the feature back on will solve all your fax problems.

Do you have a question about faxing? Send me your fax question.