Question is, if I need a few more, can I use the secondary RTS, CTS etc of the 25 pin version. If so how many are available to me ? And whether all 25 pin serial ports support these ?



Hi Raghu,
I have experience of assembling and selling assembled PC's. From my experience of assembling about 30+ PC's I can say that on allmost all modern motherboards they have 10 pin headers for serial ports with 1 missing pin in headers i.e. actually a 9 pin header. On the back side of PC even if you have a 25 pin COM port internally it may be connected to your mainboard by a 9 pin cable.
Don't just blindly assume that the 25 pin COM port at the back of your PC is actually a 25 pin version. It may be or maynot be.

Regards
Prahlad