The KX-TDA100 is the smallest and least expensive Panasonic Business Telephone System to employ UCSD (Universal Card Slot Design). UCSD allows for any available card to be inserted into any available slot in any order.
The KX-TDA100 has a total of six (6) Universal Card Slots. With UCSD technology, you can even remove the cards from a KX-TDA100 and insert them into a larger KX-TDA200 or KX-TDA600 with few exceptions. Better yet, cards can be removed and reinstalled in any of the more robust KX-TDE100, KX-TDE200 or KX-TDE600 systems. This makes the possibility of outgrowing this system, quite remote.