This harmonic oscillator controlled by crystal was found in an American documentation of the 90's. The circuit uses transistors of the time. Current equivalents can be used.
This new AMS device consists of a digital color sensor and proximity sensor that also incorporates an infrared...
This amplifier produces a few hundred milliwatts of Input 100 pF audio over a load of 4 or 8 ohms...
This transmitter for modulated infrared remote control was found in documentation from the 90s....