How does Q2 work in a JDM programmer circuit without power supply connection?

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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

and this is the description
http://www.jdm.homepage.dk/newpic7.htm"
 
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  • Schematic of a JDM serial programmer circuit with a PIC16C84 microcontroller, transistors Q1 and Q2 (BC547B), diodes D2-D7, zener diodes 5.1V and 8.2V, resistors R1 10K and R2 1.5K, and TxD, GND, CTS, DTR and RTS connections.
    newpic22.gif
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Discussion

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.