Rocket Altimeter (CB25357E)

Today we have more compact solutions. This is from a Radio Electronics magazine from October 1990. It uses the technology of the time.

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Timer 4001 II (CB15513E)
In the figure we show a timer, this simple one with only one of the four gates of integrated...
Photodiode Amplifier LM139 (CB15527E)
This circuit is a sensor for photodiodes that can be used in optical couplers, encoders and other...
Crystal tester (CB8219E)
This crystal tester was found on a 90s Ham Radio. Transistors are commonly used. The circuit is for...