The most important thing to know when working on fax machines is that fax machines as affixed to your HP, Dell, Epson, Brother, Xerox, Ricoh printers are ANALOG DEVICES. On the other hand, phone lines are becoming more and more DIGITAL as supplied by telephone/cable/TV/ISP companies. In fact, it is safe to assume that digital phones are by now in the majority in North America. So, the first question when working on fax machines is, “Is the phone company issuing a digital or an analog signal?” If analog, you can connect a phone line to the back of the fax/printer with no problem. If a digital line comes in to the building, you have to somehow convert the digital signal to analog. However, many times you will have an analog signal coming in from the ISP then it is converted to digital at your client’s or local site by some machine. In that case, you must bypass or circumvent the local digital PBX or box. This intermediary local PBX can be a point of frustration for many technicians who do not understand fax machines.
Just as a side note: Always dedicate a phone number or line for faxing only if you don’t want ping pong between receiving a phone call or fax. Yes, a fax number or line is the SAME as a phone number… No difference at all. You can use your phone number as a fax number at any time, so long as you have a machine to receive the fax with. Usually, modern printers, particularly the all-in-one machines, will have a connection/input for faxing.