Product description

As a members of the CML DuraTALK family of digital voice products, the CMX608/CMX618/CMX638 are flexible, high integration, high performance, RALCWI Vocoder, offering near toll-quality voice at very low bit rates.

  • CMX608: Half-duplex RALCWI Vocoder
  • CMX618: Half-duplex RALCWI Vocoder with Integrated Voice Codec
  • CMX638: Full-duplex RALCWI Vocoder with Integrated Voice Codec

A Forward Error Correction (FEC) engine provides optimum performance in real life applications.

The RALCWI Vocoder comprises four independent functions which are selectable by the host: Voice Encoder, FEC Encoder, Voice Decoder and FEC Decoder.

The CMX618 includes an integrated voice CODEC, offering a complete analogue voice to low bit rate vocoded data function, with integrated channel filters removing the need for external components, whereas the CMX608 requires an external voice CODEC.

All three devices operate from a dual power supply (1.8V and 3.3V) and are available in both 48-pin LQFP (L4) and 48-pin VQFN (Q3) packages.

Function Add-ins
New features or enhancements to aid Vocoder operation are available. Function Add-ins currently available:

  • Voice Store and Retrieve (VSR)
  • Noise Gate
  • Encryption
  • Fine Analogue Output Gain Option

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Devices are available through our distributors below:


Block diagram



  • RALCWI™ CML’s Digital Voice Technology
  • Near Toll Quality RALCWI™ Coding Algorithm
  • No royalty/license fee
  • Multiple Bit-Rate Modes
    – 2400 or 2750 bps
    – 3600 bps with FEC Enabled
  • 4-bit Viterbi Soft Decision Decoding
  • Integrated Voice Codec(CMX618 and CMX638 only)
  • Integrated Input and Output Channel Filters
  • 20ms, 40ms, 60ms and 80ms Packet Lengths
  • No Licensing or Royalty Payments
  • Ancillary Audio Functions:
    – Voice Activity Detector
    – Comfort Noise Generator
    – DTMF and Single Tone Regeneration
  • Voice Store and Retrieve, Encryption and Noise Gate. Fine Analogue Output Gain. Function Add-ins Available
  • Voice Activity Detector, DTMF/Tone generator, comfort noise generator, soft decision decoding


  • Digital Trunking, Digital WLL
  • Digital-voice Scrambling and Encryption
  • Voice-storage and Playback Systems
  • Messaging Systems
  • VoIP Systems
  • Voice Pagers
  • Regenerative Digital Voice Repeaters

Power supply requirement

  • 1.8V, 3.3V Tolerant I/O

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Design resources

CM608/618/638 and EV6180 Questions

Q: My EV6180 Evaluation Kit will not operate when JP2 is fitted. Why is this?

A: JP2 connects the hard-reset circuit on the EV6180 to pin 16 of the C-BUS connector J3. On the PE0003, this pin is set to input by default and a weak pull-up applied. It is possible that the reset signal will be applied until C-BUS pin 16 is actively driven low by a PE0003 script. Removing JP2 disconnects the hard-reset circuit from C-BUS pin 16. The power-on reset and the C-BUS General Reset command will function as normal with JP2 removed.

CMX608, CMX618 and CMX638 - optimising the speech quality

Optimising the speech quality using both manual and autonomous techniques to set the input gain. Go to scripts tab to download the scripts for this app note.

CMX608 and CMX618 Voice Storage and Retrieval

Voice Storage and Retrieval - using external voice-data storage

CMX608, CMX618 and CMX638 - RALCWI Vocoder - Voice Storage and Retrieve

RALCWI Vocoder - Voice Storage and Retrieve - using on-chip voice-data storage Note that this Application Note references a Function Add-In file that is available from the CMX6x8 area of the Technical Portal

EV6180 Record and Playback

Two (pes) scripts that are designed to allow evaluation of the CMX608 in the EV6180 kit. [see ReadMe file in Zip File]

CMX6x8 - Optimising the Speech Input Level on the CMX6x8

Demonstration scripts for the PE0003 and EV6180 kits. Please refer to "ReadMe.txt" for a description and supporting Application Note information.


EV6180 EV6180 The EV6180 Evaluation Kit provides the means to demonstrate and evaluate the operation of CMX6x8 full and half duplex RALCWI™ Vocoder ICs. The board is operated from a single, external power supp EV6180+EV6380_Product_Preview




DE6181 DE6181 The DE6181 is designed to assist in the evaluation of this family of products, when loaded with a Function Image™ (FI) and the CMX618 IC. DE6181_Product_Preview






C-BUS Guides

Guides to Operation and Interfacing

DE6181 Support Package

DE6181 Support Package

EV6180/6380 Board Schematics

High resolution schematics for the EV6180 and EV6380. Version C02

Package: Q3

48-pin VQFN

Package: L4

48-pin LQFP

VQFN Design Guidance Notes

VQFN Design Guidance Notes

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