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how to get 16 out from mt8870 using cd4028 IC?

i am making a robot using mt8870 dtmf ic
i have read the data sheet it says the mt8870 have 16 outputs 
how to get the 16 output 
plz check this schma ( http://www.seekic.com/uploadfile/ic-circuit/200971333450883.gif ) 
how many 4028 will be needed