Interesting! Summary: - They are using acoustic pickup for some reason (possibly for legal reasons?), there are plans on how to construct interfaces from home

Interesting! Summary: - They are using acoustic pickup for some reason (possibly for legal reasons?), there are plans on how to construct interfaces from home depot materials. - The modem is fixed speed, 300bps and uses FSK. There is no dialing, pickup/release or ring detection, this is all manual. It is RS232 lines connected to modulator/demodulator and then to phone line. - For modulator, they use NE567 which is designed as a tone decoder, but can be abused to act as tone generator instead. It can be muted by demodulator's "carrier detect", so the modem can auto-shut-off if the other side is gone. - For demodulator they use XR2211, which is apparently special PLL designed specifically for the modems. - Every other page is a full-page ad, plus there are ads inside the text, too. So 50%+ area is advertisement. If you thought that the web invented pervasive advertisements, you are wrong.