This configuration was found in the Texas Instruments optoelectronics manual. PNP transistors support equivalents and the phot transistor does.
Placed in the vicinity of a telegraphic transmitter (CW), this circuit produces an audible signal on...
Damped oscillators can be used to produce sound from percussion instruments such as the triangle, bell,...
We found this circuit in a 1983 English magazine, but it can be easily assembled with the BC548...