Thanks, can you name them?
Name what? Name the additional sensor part numbers?
Currently the only additional sensor supported is the temperature/humidity sensor part number WH31 or WH31B. Realize this is different than the included WH32B that has temperature/humidity and pressure. You can only have one WH32B.
The difference between WH31 and WH31B is that the B version does not include a RCC (Radio Controlled Clock). The WS-2000 does not need a clock at all on the optional sensors. So you can use either the WH31 or the WH31B but it will be a bit less costly to get the B version. The RCC is currently only required for the WS-3000 station model for some reason. So the WS-3000 can't use the WH31B. The ObserverIP can use either the WH31 or WH31B as additional sensors. The ObserverIP requires a WS-1000-BTH as a primary indoor/humidity/pressure sensor. I don't know if the ObserverIP is compatible with the WH32B.
In summary:
WH31 - Additional Temperature and Humidity sensor with RCC (you can have up to 8 )
WH31B - Additional Temperature and Humidity sensor without RCC (you can have up to 8 )
WH32B - primary Temperature/Humidity and Pressure sensor (you can only have one that comes with WS-2000)
WS-1000-BTH - Temperature/Humidity/Pressure sensor primary for ObserverIP
* The WS-2000 and ObserverIP do not use the RCC feature of the additional WH31 sensors, so it works but that part is ignored.
* I don't know if the WH32B is a compatible replacement for the WS-1000-BTH that the ObserverIP uses as a primary.