How can I figure out where the fax machine connects in the right plug?

Our internet went down for two days.The office phone is working now (253) 838-2620, but can't get the fax and merchant machine to work (253)-210-3531.. They are suppose to be on a separate line. Now I need to hook up the fax machine and the merchant machine and I can't figure out the right way to do it. Usually, we use the line for both by just switching back and forth. The fax machine is a Canon Faxphone L80, and the merchant machine is a Nurit 2085. Every plug I have tried on the Linksys Router doesn't give me a dial tone. What do I do now?