Based on TTL logic this circuit can vary both the frequency and the pulse width of a rectangular signal. Equivalent components can be tested.
Found in a 1960s documentation, this circuit uses a transistor to drive a relay as well as a set...
This approach alarm was found in Radio Electronics from July 1990. The circuit must be powered by a...
This 75 W power supply was found in American documentation from the 1980s. Transistors can be...