HT9020B -- Call Progress Tone Detector General Description The HT9020B call progress tone detector is a telecom peripheral for Auto-dialing system use. Switched capacitors technology is implemented into the chip to get good performance characteristics of band pass filter in the range of 305 to 640Hz call progress tone which is dual tone multi-frequency signal. When it detected CPT signal then it generates relative envelopes for external microcontroller decision to finish different kinds of CPT signal detection such as dial tone, busy tone, ring-back tone and reorder tone. 上海辰祥电子科技有限公司 联系人：周平 13917885749 Features Operating voltage: 2.5V to 5.5V Low power consumption Low cost 32768Hz crystal CPT Band: 305~640Hz detection Good performance: -8 ~ -39dBm at VDD=2.5V 0 ~ -27dBm at VDD=5V 8-pin DIP/SOP packages