This circuit was found in documentation from the 90s. The transistors can be general-purpose equivalents. The circuit has two versions, one that drives LEDs and another that drives a relay as a load.
This small blocking oscillator for approximately 1000 Hz was found in an American documentation from the...
An audio signal is applied to the input of this circuit. Depending on the position of the selector...
Using only one LM107 operational amplifier, National Semiconductor suggests the circuit in the...