The WS2902a display unit has built in T/H/Barometer sensors.
The WS-2000 display unit itself does not have a built in T/H/Barometer sensor. The kit comes with an external unit that has the T/H/Barometer sensors. This unit can be placed anywhere with in range of the display. The display shows the T/H readings as Indoor Temperature and Indoor Humidity in the upper right hand corner of the screen. I would guess they did this to keep any internal heat from the display from throwing off the temp reading.
If you have any additional T/H sensors (up to eight) they will also be displayed in the same spot on the screen. You can edit the label for what is displayed for each additional sensor. You can set which sensor is displayed, manual cycle which is display, or have it auto cycle them.
In my case I have two additional T/S sensors that I put in my refrigerators and I have labeled then "Kitchen Fridge" and "Basement Fridge". I have the display set to auto cycle showing them on the screen.