Fifteen ways of carrying data as sound, each one generating a real signal rather than an impression of one — the tones, timings and framing are as specified, so the output decodes in software written for the actual protocol.
AX.25 frames carry a genuine X.25 frame check sequence, bit stuffing and NRZI, so a
TNC or direwolf will decode them.
ZX Spectrum output is a header and data block pair for a CODE file, checksummed —
LOAD "" CODE loads it.
Commodore 64 blocks are written twice with the KERNAL's two sync countdowns. The leader is shortened by default to keep files small; raise it for real hardware.
V.22 sweeps its phase across a quarter of each symbol in place of a full root-raised-cosine pulse shaper — close enough to sound and decode right, short of what a modem chip would transmit.
Morse and PSK31 are shaped so they do not click or splatter; everything else is phase-continuous by construction.
Multi-channel CW is the sum of its channels and nothing else — each one is the same keying the single-tone mode writes, so a filter narrow enough to sit on one tone reads that channel back on its own. The mix is scaled by a single number afterwards so that channels keyed at the same instant cannot clip.
ClackDem decodes thirteen of these modes from a file or live from the microphone. Send a signal across with To Recorder, or put the two windows side by side and let it listen to the speakers.
Signals are capped at three minutes — a long message at 45 baud is a very long file. V.22 DQPSK and multi-channel CW are encode-only; everything else can be read back.