name:         HT93215BL
function:     1-Memory Tone/Pulse Dialer
package:      DIP20,20
manufacturer: Holtek

       +--()--+
  LOCK | 1  20| NC
   HFO | 2  19| HFI
  HKSB | 3  18| R4B
  MODE | 4  17| R3B
    X1 | 5  16| R2B
    X2 | 6  15| R1B
   VSS | 7  14| C3B
   VDD | 8  13| C2B
  DTMF | 9  12| C1B
XMUTEB |10  11| POB
       +------+


This pinout came from the Chipdir:
http://www.chipdir.org/