I have a bunch of Kenwood TK-2100 VHF radios that are re-programmable via the serial port. I have a DOS-based application that works with the radios, but is only reliable with computers with two ...

So I'm trying to detect through Visual Basic 6.0 when a voltage change occurs on one of the pins of the serial/parallel port. The whole thing is pretty simple; no data transfer/handshaking/etc ...

But the problem is that an RS232 serial port operates with 12V logic levels and the JTAG side of the programmer needs to operate with the logic levels native to the device you’re programming.