My parents had a TRU8866 (2-line) base, but lost the handsets. We bought 3 new TCX805 handsets, but none of them would register on the base. When placed on the base, the display would say "connecting" but never register. The message would then return to the default "models vary!..." message. Since then, we have purchased a new base to see if that was the problem, but still nothing. Both manuals indicate that the two models are compatible, but we can't get it to work!

Lands Phones - Uniden - TCX805 Cordless Expansion Handset