The transistor used in this circuit is uncommon today. AC124 or equivalent such as AC188K and 2N2431 can be used. The circuit is from the 80's and makes use of transformers.
This simple timer based on unijunction and SCR transistors is from 1995 documentation. The maximum...
This configuration with complementary transistors causes an LED to flash at a frequency that is...
An interesting application that can be implemented with the LM139 is the pulse width modulator. This is...