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Calling Line ID plus Dial Tone Decode for VMWI

CMX612 - (Voice-Message Waiting Indicator)



  • Bellcore, British Telecom and ETSI 'CLI and CIDCW' Compatibility
  • Tested to Bellcore SR-3004
  • CLI, CIDCW and VMWI Decoder for Multiple Extension Interworking (MEI)
  • Exceptional Talk-Off/Talk Down Performance
  • CPE Alerting Signal Detector
  • 'Zero Power' Ring or Line Polarity Reversal Detector
  • V.23/Bell 202 FSK Demodulator with Data Retiming
  • µC Interrupt/Wake-Up Output
  • Low Power Operation (2.7V)


  • CLI and CIDCW Feature Phones and Adjunct Boxes
  • Analogue Display Services Interface (ADSI) Units
  • Voice-Mail Indication Equipment
  • Extension Units or CLI Units
  • Computer Telephone Integration
  • Call Logging Systems

Supply Requirement:

  • 2.7 to 5.5 V power supply

The CMX612 is a low power CMOS integrated circuit for the reception of physical layer signals used in British Telecom’s Calling Line Identification Service (CLIP), Bellcore’s Calling Identity Delivery system (CID), the Cable Communications Association’s Caller Display Services (CDS) and similar evolving systems.

It also meets the requirements of the emerging Caller Identity with Call Waiting services (CIDCW) specification.

In addition, it provides Visual Message Waiting Indicator (VMWI) detection in both CLASS (FSK) and (SDT) Stuttered Dial Tone modes.

Two different signal inputs are provided to the device, to support Tip/Ring and Hybrid connectivity.
The device includes a ‘zero-power’ ring or line reversal detector, a dual-tone (2130Hz plus 2750Hz) Tone Alert Signal detector, a dual-tone (350Hz plus 440Hz) stuttered dial tone detector and a 1200-baud FSK V23/Bell202 compatible asynchronous data demodulator with a data retiming circuit which removes the need for a UART in the associated µController.

The CMX612 is suitable for use in systems to BT specifications SIN227 and SIN242, Bellcore GR-30-CORE and SR-TSV-002476, CCA TW/P&E/312, ETSI ETS 300 659 parts 1 and 2, ETS 300 778 parts 1 and 2 and Mercury Communications MNR 19.

Block Diagram

CMX612: for the reception of CLIP, CID and CDS wireline signals

Design Support Information

C-BUS Guides Guides to operation and interfacing
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