Product description

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

  • 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, which removes the need for external components.

Both 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:


  • SalesNetworkLogo_2
  • Mouser_logo
  • RFMW logo

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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We can tailor an existing product to your unique requirements

Design resources

Package: Q3

48-pin VQFN

Package: L4

48-pin LQFP

VQFN Design Guidance Notes

VQFN Design Guidance Notes




The PE0003 Evaluation Kit Interface Card is a global interface system for use with evaluation kits for CML’s new generation ICs, including FirmASIC™ based products. This greatly simplifies the approach to the evaluation and design-in process.




EV6380 board image

The EV6380 Evaluation Kit allows rapid and full evaluation of the CMX638 and can also be used in half-duplex mode to demonstrate the operation of the CMX618.

Product Preview

EV6380 User Manual


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.

EV6380 Hi-Res Schematic

EV6380 Hi-res schematic for board version C, MOD state 2. – Download


Full-duplex speech demonstration on the EV6380 Evaluation Kit. – Download

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