Description
The HC-55564 is a half duplex modulator/demodulator CMOS intergrated circuit used to convert voice signals into serial NRZ digital data and to reconvert that data into voice. The conversion is by delta-modulation, using the Continuously Variable Slope (CVSD) method of modulation/demodulation.

Features
• All Digital
• Requires Few External Parts
• Low Power Drain: 1.5mW Typical From Single 4.5V To 6V Supply
• Time Constants Determined by Clock Frequency; No Calibration or Drift Problems: Automatic Offset Adjustment
• Half Duplex Operation Under Digital Control
• Filter Reset Under Digital Control
• Automatic Overload Recovery
• Automatic “Quiet” Pattern Generation
• AGC Control Signal Available

Applications
• Voice Transmission Over Data Channels (Modems)
• Voice/Data Multiplexing (Pair Gain)
• Voice Encryption/Scrambling
• Voicemail
• Audio Manipulations: Delay Lines, Time Compression, Echo Generation/Suppression, Special Effects, etc.
• Pagers/Satellites
• Data Acquisition Systems
• Voice I/O for Digital Systems and Speech Synthesis Requiring Small Size, Low Weight, and Ease of Reprogrammability
• Related Literature - AN607, Delta Modulation for Voice Transmission