Found in a 1967 Electronic Design, this circuit changes the phase of a signal in 8 different ways, given by the formulas next to the diagram. Equivalent general-purpose transistors can be used.
This power supply may have 5, 6, 9 or 12 V outputs depending on the 78XX and 79XX series...
This simple amplifier uses a microphone attached to the telephone. The 3-transistor circuit was...
This 80's circuit can be made with current comparators. Rectification accuracy is 1% DC up to 100...