We found this circuit in an old documentation, but it is still current. General purpose transistors can be used, and the SCR can be the TIC106. The bell is a transducer with an oscillator (buzzer).
This lamp flasher configuration using an astable multivibrator is from a 1968 publication. The...
When the voltage in the circuit exceeds the value set in the trimpot, the LED goes off and, if a...
The maximum input voltage of this circuit is 20V and the output current is 250 mA. The circuit is from...