First, I cannot find any references such as you describe on page 207 ofThe DCS Companion 3rd Edition or, for that matter, on any page of the book.

Regardless, the required serial splitter would have 1 male end and 2 female ends so as to allow the TIU's female serial port to be split into a pair of female serial ports.

The only references I can find to the serial "Y" cable are in The DCS WiFi Companion 2nd Edition, and both references are correct:

• Page 42: "If using a USB to Serial cable and the TIU is already connected to a Lionel command base, then a serial "Y" cable (1 male end, 2 female ends) will also be required."
• Page 221: "However, if a TIU other than a Rev. L is used, connect the TIU’s serial port to both the WIU and the other device using a 9-pin, serial “Y” cable that has 1 male port and 2 female ports."

Here is a copy of the book, and the pasted in pages of the updates you released on the OGR forum after the book was published I printed out all the updates/corrections and pasted them into the book on the correct pages ; Just in case you wanted to update this update!

Regardless after I looked at the cables on line and the TIU and inputs I figured it had to be the other way around as you have described above. I called a lot of local computer and used computer stores but could not find it, so have ordered off a internet store will be  few days till it gets here.

As I have been reading more of the details of the WI Fi and TIU and updates from recent posts and updates from when I first installed the WI Fi system with difficulty making it all work well.  I am putting my version L TIU in the main 3 rail train room where I have a vast fleet of DCS MTH engines and only a couple of TMCC and only using the Hand held remotes, adding a few more while they are still being made; prefer the feel of these so you do not have to look at a screen all the time. I do like the buttons that I can feel without looking at a screen all the time for running the MTH engines.  I recently started another layout in a different part of the house and have several Lionel TMCC trains I want to run on this layout (2 rail scale) so will add the TMCC base here and only use the Wi Fi and Lionel remote for this room, have an older TIU to use for this layout.  Hoping I can get the MTH WI Fi system to work better here, with the suggested practices of only using all WI FI or all remotes. I do not normally run both layouts at the same time. But hoping there is no interference if running both  layouts for operating sessions or open houses. 

iboThe updates that you pasted into your copy have been superseded by newer versions of the book.

The latest copy of The DCS Companion 3rd Edition, dated March 2017, has the correct statement of "1 male end and 2 female ends".

Here's an extract of the latest copy of the eBook from MTH's Shopatron/Kibo site, downloaded just a few minutes ago:

The DCS Application requires the following MTH DCS devices in order to operate:

• DCS 5.0 or later and DCS Loader Program 5.0 or later
• #50-1003 DCS TIU
• #50-1002 DCS Remote (for functions not present in the application)
• #50-1034 WiFi Interface Unit
• USB cable (for Rev. L TIU), male USB-B (TIU end) to male USB-A (WiFi Interface Unit end); or USB to Serial cable (for all other TIUs). If using a USB to Serial cable and the TIU is already connected to a Lionel command base, then a serial "Y" cable (1 male end, 2 female ends) will also be required.