name: HT9020A function: Call Progress Tone Decoder & ABR Controller package: DIP/SOP18,18 manufacturer: Holtek +--()--+ DEC/ABRCB | 1 18| VDD OEB/HKOFF | 2 17| BUSY/BREAK ENV/END | 3 16| RBK/KEY2 DV/LED | 4 15| DIAL/KEY1 RTZ/SEL1 | 5 14| ENB/KEYB VREF/SEL2 | 6 13| CLRB SIN | 7 12| X2 B3/RING | 8 11| X1 VSS | 9 10| TEST +------+ This pinout came from the Chipdir: http://www.chipdir.org/