We found this configuration in a 1990 Poptronics. The circuit can be powered by voltages between 6 and 15 V, changing the resistors in series with the LED. The frequency is set at R7.
This simple transistor tester uses a common 3 mA analog instrument that has its scale changed as...
This circuit was obtained from an English publication from the 70's. The circuit is still current for...
This commercial circuit N-101 was obtained in a Japanese publication from 1971. It is a typical...