Description
The MT9092 HPhone-II is a fully featured integrated digital telephone circuit which includes an HDLC data formatter. Voice band signals are converted to digital PCM and vice versa by a switched capacitor Filter/Codec. The Filter/Codec uses an ingenious differential architecture to achieve low noise operation over a wide dynamic range with a single 5V supply. A Digital Signal Processor provides handsfree speaker-phone operation. The DSP is also used to generate tones (DTMF, Ringer and Call Progress) and control audio gains. Internal registers are accessed through a serial microport conforming to INTEL MCS-51™ specifications. The device is fabricated in Mitels low power ISO2-CMOS technology.

Features
• Programmable µ-Law/A-Law codec and filters
• Programmable CCITT (G.711)/sign-magnitude coding
• Programmable transmit, receive and side-tone gains
• DSP-based:
   i) Speakerphone switching algorithm
   ii) DTMF and single tone generator
   iii) Tone Ringer
• Differential interface to telephony transducers
• Differential audio paths
• Single 5 volt power supply
• X.25 Level 2 HDLC data formatting

Applications
• Fully featured digital telephone sets
• Cellular phone sets
• Local area communications stations