A technique by which two voice grade services and two different telephone numbers can coexist on the same local loop through frequency division multiplexing (FDM).The two numbers can be associated with two different voice numbers or one number can be a fax number and another a voice number, with distinctive ringing patterns distinguishing fax calls from voice calls.The fax machine can be programmed to recognize the fax ringing pattern and to answer those calls automatically. See also distinctive ringing, FDM, local loop, and voice grade.
A technique defined by the Federal Communications Commission (FCC) by which an incumbent local exchange carrier (ILEC) provides voice grade telephone service over a local loop, and shares that loop with a competitive local exchange carrier (CLEC) that provides digital subscriber line (DSL) service. Line sharing is accomplished through frequency division multiplexing (FDM). See also CLEC, FCC, FDM, ILEC, local loop, and voice grade.