Gerardo,
Consider having your fax line carrier add a delayed call forwarding feature to go to your Updox 800 number if your fax line is busy/not answered for 4-5 rings. This should be a free service.
If someone is trying to fax you, and the line is busy on another fax, it will get forwarded to Updox. You can tell the carrier how many rings you want their system to wait before it call forwards to Updox. You get 500 incoming faxes a month included in the base fee, so you might get several a week. More importantly, people faxing you will never get a busy line and forget to fax you later with something you should have had immediately.
It is like having a backup fax line provided free in your Updox plan.
