

And unfortunately, the T400 does not appear to have the middle connector in the Ultrabay necessary for the serial / parallel adapter.
IBM USB SERIAL PARALLEL ADAPTER 22P9035 UPDATE
Update : I finally got to see a ThinkPad T400 in person.

The adapter uses the middle connector in the Ultrabay. When the adapter is inserted into the Ultrabay, the serial and parallel ports will show up in the device manager and in the BIOS. Some of the older ThinkPads have a parallel port, and you will have to use the docking station to get a serial port. The adapter does not work on the R61, any of the Z series, or anything older than the 6x series. IBM Support IBM UPS 7500XHV and 10000XHV Serial to USB Adapter Driver.
IBM USB SERIAL PARALLEL ADAPTER 22P9035 DOWNLOAD
It's an Ultrabay Slim device that works on the T60, T61, and R60. VIDEOS 360° VIEW IMAGES IBM USB Serial/Parallel Adapter Visit the Lenovo Store. Download the lastest IBM UPS 7500XHV and 10000XHV Serial to USB Adapter Drivers. This is where the ThinkPad Serial / Parallel Port Bay Adapter comes in. Sometimes USB converters work, but they are problematic, especially if you need to use older programs that are written to talk directly to the hardware. Ibm-usb-serial-parallel-adapte r-driver-22p9035 //TOP Download File Link, File Size, File Description. Most modern notebooks (or even desktops) don't have serial or parallel ports, making configuring management routers and switches and industrial machines like PLC's or HMI panels extremely difficult or impossible.
