A Teen line makes you home phone ring with a different cadence if some calls this 2nd number. It is like having 2 phone numbers tied to one phone line. BTES sets the 2nd number or teen line to ring with a cadence of “Long-Long”. If you have a fax machine that supports this you can set it to pick up only when it hears the “Long-Long” Ring cadence. Please contact your fax machine manufacture if you need help setting up your fax machine for this feature.