One way intercom...help

I am using this circuit and simply (I think ) remove S1 so S2 can be used so that its 'one talks and one listens'..one way. I think I have it right, but I was asked to explain in depth the operation. My explainations are useless. Does someone with a more analytical mind have calculations I could show my son to help.
Thanks

What experience has your son with electronics?

We need a starting point....

experience

A fair bit, he has been getting into 555 timers a bit, mainly calculating stuff so he wants to analyse a real circuit and see calculations too

The circuit won't work because the transistor is incorrectly biased and is saturated.

My corrected circuit has a transistor named that has a DC current gain from about 100 to 300.
It has the base bias resistor connected to the collector for DC negative feedback.

1) If the gain of the transistor is 100 then the collector voltage is 6.2V.
2) If the gain of the transistor is 300 then the collector voltage is 3.4V.