modems, are referred to generically as Bell 202 modulation, and any device employing it as Bell-202-compatible.

* Bell 202 AFSK uses a 1200 Hz tone for mark (typically a binary 1) and 2200 Hz for space (typically a binary 0).

In North America, Bell 202 AFSK modulation is used to transmit Caller ID information over POTS lines in the public telephone network.