Judging by what you have said there bart, your still not connected *via* the phone. Your all-in-one printer is connected directly to the phone line, so you will have no problems. The only clause is that if your line is actually digital. Digital lines can often be found on corporate networks such as Avaya. Many phones can often be mistaken as digital phones, just because they have a lcd screen on them does not make them a digital phone. It is still an analogue signal.
If your line is analogue (if your at home, then it will be), then best practice is to connect both lines directly to the wall, and using a splitter (as there are also different types of telephone cable):
EDIT: Marked as Answered.