This circuit triggers by choosing the higher of two voltages. The circuit is from a 1964 Electronic Design. The transistors are of the time and can be replaced by current equivalents.
This small crystal microphone transmitter was indicated in an 80s spy book. The range depends on...
This circuit, found in a 1978 publication, converts 5 V into a symmetrical 15 V output under low...
The configuration shown in the figure is one of the most traditional when it is desired to produce...