This circuit also appears elsewhere on this site, obtained from other sources. This is an 80's American schematic book. Instead the lamp can be used white high-brightness LEDs.
Suitable for general use and alarms, this Hartley oscillator circuit from a 1960's Gernsback...
Found in a 90s Popular Electronics, it serves both TTL and CMOS logic. The injector can provide 10...
This filter with the operational 741 passes the frequency range between 300 Hz and 3,400 Hz. This...