Very slow frequency modulation. Slow enough you could hear the tone change slightly as it shifted modulation every few seconds.
Frequency Shift Keying is the more accurate term for this, as it’s not a continuous shift up and down of the frequency like you’d get with FM radio, it’s stepped.
If you imagine a higher tone being decoded a “1” and a lower tone being a “0”, basically it was something like that. Listen long enough and you’d get enough 1s and 0s to build up a message.
i just had an image of an early nondigital version of this. some unwashed musician you hired sitting at the bottom of the shaft with an earpiece jumps up ITS AN EFFF SHARP EVERYBODY RUN
Very slow frequency modulation. Slow enough you could hear the tone change slightly as it shifted modulation every few seconds.
Frequency Shift Keying is the more accurate term for this, as it’s not a continuous shift up and down of the frequency like you’d get with FM radio, it’s stepped.
If you imagine a higher tone being decoded a “1” and a lower tone being a “0”, basically it was something like that. Listen long enough and you’d get enough 1s and 0s to build up a message.
i just had an image of an early nondigital version of this. some unwashed musician you hired sitting at the bottom of the shaft with an earpiece jumps up ITS AN EFFF SHARP EVERYBODY RUN