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 circuit, which uses components still common today, was found in a 1997 documentation. It...
This circuit with its light source was found in American documentation two years 70. Or...
This circuit was found in a Philips documentation from 1966. The circuit provides 1 mW with a...