OS X Leopard and USB to Serial driver

Hi I need to work with a router using a usb to serial converter
I had installed all this 3 drivers
http://sourceforge.net/projects/osx-pl2303/

http://serialio.com/products/adaptors/usb_serial.php

http://www.keyspan.com/downloads/

and they doesn't work, I do ls /dev/tty.* in terminal but I don't see a new thing there, I only see:

/dev/tty.BlackBerry8130-BlackBer-1 /dev/tty.Bluetooth-PDA-Sync
/dev/tty.Bluetooth-Modem

I'm following this instructions:
First, open Terminal. If you've never used it before, it's under Applications/Utilities/Terminal. Next, type

ls /dev/tty.*
to get a list of all of your serial ports. Pick the one that you want to open. For example, my list looks like this:

/dev/tty.BTRS232 /dev/tty.Tigoe6630-AppleAgent-1
/dev/tty.Bluetooth-Modem /dev/tty.Tigoe6630-Dial-UpNetwor-2
/dev/tty.KeySerial1 /dev/tty.modem
And I know from previous experience that /dev/tty.Keyserial1 is my Keyspan USB-to-serial adaptor. It's connected to a PIC at the moment. The PIC's programmed to read one byte of serial data at 9600 bits per second, then send back three bytes, "A", "B" and "C".

Knowing the serial port, you can just type screen portname datarate to show the serial data on the screen. In my case, it was:

screen /dev/tty.Keyserial1 9600
Then I started typing bytes at the PIC, and it sent bytes back to me. Whee! No need for zTerm! To quit the screen app, tyoe control-A, then control-\.

any help, please?