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[SOLVED] What is the role of this transistor?

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VTI_16V

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Hello people :). Can someone explain to me what is the purpose of this bc817 transistor in this buzzer circuit? Thanks a lot
buzz.jpg
 

It's a current limiting circuit, but the selection of component values seems questionable.
 
Can you explain me how this works? What i can see from this, when TR2 receives positive pulse it turns on and it connects ground to buzzer... What happens to TR1 and how it limits current, i dont get it :(... Current through buzzer turns TR1 on?
 

Current of the buzzer in the emitter resistors of TR2 turns on TR1 which reduces the base voltage if TR2 so that the buzzer current is limited.
 
i got it now, thank you :)
 

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