This space mark demodulator for FSK signals was found in an American telecommunication documentation from the 1980s. The circuit operates with 2025 Hz and 225 Hz mark space signals.
This circuit, when triggered, locks, and remains so until the source is switched off for a moment or...
With an op amp with FET, this 1977 circuit uses an LDR as a sensor and drives a relay. The relay...
This low power bass booster is from the 1977 National Semiconductor Audio Handbook. The circuit is...