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You could really hear the noise with these however. And there's the fact that the speaker was directly touching the microphone. It's cool that this works basica
by michaelmior 13y ago
You could really hear the noise with these however. And there's the fact that the speaker was directly touching the microphone. It's cool that this works basically inaudibly across a room.
- nknighthb 13y agoYou could hear them because they were constrained to the voiceband. Frequencies outside 300-3400Hz were deliberately filtered out by the telephone system to maximize the number of calls that could be carried on a limited amount of copper. "Across the room" isn't really interesting, either. I've decoded PSK31 across a room. Higher, near-inaudible frequencies would probably make the decode even cleaner.