We found this circuit in December 1986, Radio Electronics magazine. It uses 3 inverters and has the frequency determined by the crystal. The power supply is 5 V.
This simple circuit controls the brightness of an LED from LDRs, NTCs, PTCs or other resistive sensors....
This remote listening device was found in documentation from the 50's. The transistors used are...
This circuit came out in a Modern Electronics from June 1990. In it we have a low frequency...