Need help to understand this circuit

[aruna1]

this is the circuit of JDM programmer.
I'm trying to understand how Q2 works here.coz only base of Q2 get a voltage and emitter or collector is not connected to power supply,

there is a description about this circuit,but I can't understand that description.

here is the circuit

http://img17.imageshack.us/img17/322/newpic22.gif [Broken]

and this is the description
http://www.jdm.homepage.dk/newpic7.htm"

 

[vk6kro]

The Micro being programmed can supply voltage or connect the RB7 port of the chip to ground.

The connections at the right hand side of the diagram refer to a serial RS232 port on a computer which can also supply power.

So, the transistor Q2 gets its voltages from these sources and it operates sometimes as a common base amplifier and sometimes as an emitter follower, which is a neat trick.

You would have to know the programming software to work out the exact processses involved, but the description seems to describe the function of this transistor adequately.