Remote control tester (CB7823E)

This circuit from a 90s Electronics Now, uses a 4010 gate as a signal amplifier. The circuit triggers an indicator LED.

Universal Battery Test (CB21347E)
This circuit was obtained from an English circuit manual. Components are common and LEDs can be 3...
Linear VCO (CB9429E)
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...
100 kHz to 1 MHz Oscillator (CB12815E)
This circuit can generate signals from 100 kHz to 1 MHz depending on the L1 coil. For the medium...