This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
This circuit triggers an oscillator when any of the sensors is opened. The circuit can be powered by...
This circuit imitates the singing of a bird intermittently with the intermittency determined by C1...
This is a high gain circuit with 3 transistors connected in direct coupling. The circuit is from a...