Practice code oscillator (CB21696E)

In the figure we have an astable multivibrator driving a speaker to produce audio signals for Morse code practice.

Class A Amplifier - 2N3055 (CB1002E)
I found this circuit in an article in a 2003 publication. The circuit is an example of how to...
Simple SCR alarm (CB22090E)
This circuit drives a buzzer or electric buzzer but can be used to trigger a relay or other load....
BCP56H Medium Power NPN Transistors 80 V 1 A
May 2017 - Mouser Electronics is already in stock with the new BCP1395 transistors from Nexperia....