This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
Different delays for the rise time and fall time of the output signal when compared with the input...
This simple general-purpose transistor mixer was taken from an article in Electronics Now magazine in...
September 2017 - Würth Elektronik High Power Ultraviolet LEDs can be obtained from Mouser...