name:         HT9315AV
function:     15-Memory Tone/Pulse Dialers with Volume Switches
package:      DIP20,20
manufacturer: Holtek

       +--()--+
    S1 | 1  20| S2
   C1B | 2  19| R4B
   C2B | 3  18| R3B
   C3B | 4  17| R2B
   C4B | 5  16| R1B
   C5B | 6  15| MODE/KT
    X1 | 7  14| DTMF
    X2 | 8  13| POB
XMUTEB | 9  12| HKSB
   VSS |10  11| VDD
       +------+


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