Ignition switch information needed please
 

Car is a 1984 Carrera Targa.
I know there is a warning buzzer fitted to the car but I am trying to understand how it functions. I have studied Bentley’s but I am confused and concerned it may not be correct.

So what causes the buzzer to sound? Is it insertion of the key into the ignition if a door is open? Or????

If it is key insertion what in the switch makes the circuit?

Thanks for any and all input to help me solve this issue

Peter