Heat Pumps and Electric Heating - Hlp with Trane and Robertshaw

i have a trane XL14i heat pump with a variable sp handler twe065 with aux and emg strips. i want to connect a robertshaw 9870i programmable t'stat up to get the most out of the handler and comfort R settings. The trane has terminals G O B W3 W2 W1 R BK T Y YLO. What are the W3 BK YLO for? And is B common?
The new T'stat has C G Y1 B E O R W2 Y2 L H D
Thanks,

W3 is *normally* an economizer or dehumidifier. B is the reversing valve, just like O is, except with B the reversing vale energizes to go into heat, where as with O it energizes to go into cool. I fyou have a Trane you will use O. C is common. BK should connect to a humidistat if you have one, if not jump BK and R together. I'm not sure about YLO.

All you should need is R C G O Y1 W1 W2 unless you have a humidistat, or an economizer/dehumidifier installed.

Bloodstone, Thanks a bunch....
If my T'stat has a D terminal for Dehumidity Relay can I just hook it up to the W3 or would I have to run it to w3 with a jumper going out to the outside unit? Reason is my unit short cycles in the summer and the Humidity has been as high as 65-70%. I want the unit to remove it instead of relying on a stand alone dehudmidifier. I get 44+ pints a day + what the AC gets out in the summer. A load clac was done and it was right a 4.5 ton so they bumped it to 5 because of the heatpump (that I cannot get use to). That's why I'm so interested in the ability of the stat and Trane unit.
Thanks again for your help.