An opening of 2D shows a balanced hand of 19-21 that may have a weak five card major. Responder responds as follows

0-4: 

• pass with diamonds
• 2H transfer to 2S over which responder may pass, or signoff in clubs or heart
• 2S transfer to 2NT 

5-6: 

• 2H transfer to 2S, and the responder bids 2NT 

7+: 

• 2S transfer to 2NT and then raise to 3NT showing balanced 7-9
• 2NT shows balanced 10+
• 3x shows 10+ and a broken suit