When signals are transmitted from one
modem to another, each modem
interfaces at a specific speed. If one modem communicates at a faster rate than the modem at the other end, then the faster modem falls back to a slower
modulation. For example, if a user connects to the Internet using a 14000-
bps modem and attempts to
download a file from a user who is connected to the Internet at 2400-bps, modulation fallback occurs and the two modems will only be able to communicate at the slower speed because that is the highest speed they have in common.