We found this circuit in a Radio Electronics issue from July 1969. The lamp remains on until C1 opens. The time is given by capacitor C1.
This circuit uses a TL071 to differential amplify the signals from a microphone and thus reduce...
We found this circuit in a 1995 publication. It makes use of infrared LEDs of the type existing at...
This circuit is from September 1984 Radio Electronics. The frequency can be changed by changing C1 and...