CML's Digital Voice products support voice-data (generation/decoding) functions for digital radio systems and the many
other in-band audio applications where there is a need for storage, playback and manipulation.
CML's CVSD products offer a flexible compand algorithm with programmable sampling clocks, data rates
and force-idle operation.
CML's RALCWI based ICs provide near-toll-quality voice performance at very low bit rates.
- Design solutions for digital voice products
- Product design consultancy
- Help desk teams to support design
< < < < < Please use the links on the left to view the relevant product overviews
Flexible, half-duplex, highly integrated RALCWI vocoder and CVSD ICs suited to such wireless and wireline voice applications as voice scramblers, alarm systems, military field applications and digital professional and leisure two-way radios.
Robust Advanced Low-Complexity Waveform-Interpolation (RALCWI) and Continuously Variable Slope Delta (CVSD) products and functions are described in the table below:
| Product | Data Type | Audio Features | Supply |
|---|---|---|---|
| CMX608
Half Duplex RALCWI Vocoder |
RALCWI
2050, 2400, 2750 b/s 3600b/s with FEC |
Voice Activity Detector
Comfort Noise Generator DTMF and Tone Generator |
1.8V (3.3V tolerant I/O) |
| CMX618
Half Duplex RALCWI Vocoder with Audio Codec |
RALCWI
2050, 2400, 2750 b/s 3600b/s with FEC |
Voice Activity Detector
Audio Codec Comfort Noise Generator DTMF and Tone Generator |
1.8V (3.3V tolerant I/O) |
| CMX638
Full Duplex RALCWI Vocoder with Audio Codec |
RALCWI
2050, 2400, 2750 b/s 3600b/s with FEC |
Voice Activity Detector
Audio Codec Comfort Noise Generator DTMF and Tone Generator |
1.8V (3.3V tolerant I/O) |
| CMX649
Adaptive Delta Modulation (ADM) Voice Codec |
ADM, PCM and CVSD
16 to 128 kb/s |
Input and Output
Bandpass Filters |
2.7 to 5.5 V |
| CMX639
CVSD Voice Codec |
CVSD
8 to 128 kb/s |
Input and Output
Bandpass Filters |
2.7 to 5.5 V |
| MX629
'Military' Delta Codec |
CVSD
16, 32 and 64 kb/s |
Input and Output
Bandpass Filters |
4.5 to 5.5 V |
| FX/MX619
'Eurocom' Delta Codec |
CVSD
16, 32 and 64 kb/s |
Input and Output
Bandpass Filters |
4.5 to 5.5 V |
Adaptive Delta Modulation (ADM) Example
The DE6491 is a CMX649-based wireless voice link demonstration kit that demonstrates CMX649 ADM
Codec IC operation in a low-power, cordless headset application.
Operating as a short range RF device in the 863 to 865 MHz European licence-exempt band,
this demonstration kit consists of two separate stand-alone PCBs each with the following sections:
CMX649-based audio, RF transceiver and control.
The basic design may be user adapted to other RF frequencies. Full-duplex voice operation at up to
20 metres range is provided via a single RF channel Time Division Duplex (TDD) link.
With the supplied headsets a user can investigate two-way voice-audio transfer between units.
Each PCB can be powered, standalone, from a choice of AAA batteries or a bench power supply.
Intelligent powersaving reduces supply current when not communicating.
The DE6491 Wireless Voice-link Demonstration Kit
RALCWI Vocoder Example
The EV6180 and EV6380 Evaluation Kits provide the means, in the form of pcb based kits, to demonstrate
and evaluate the operation of CMX6x8 family of full and half duplex RALCWI Vocoder ICs.
Each PCB can be controlled with via a PC runnning a (CML) PE0002 EvKit Interface Card and ES0002 GUI software.
This software is available from the CML website.
The board circuits are powered from a single, external power supply. On-board voltage regulators provide the
required analogue and digital supply voltages.
Connectors are provided to allow direct interfacing to the C-BUS and SPI interfaces on the CMX6x8 devices.
The on-chip audio codec (CMX618 and CMX638) is accessible through two 3.5mm stereo jack sockets.
The audio codec signal paths can be configured as single-ended or differential.
The EV6180 Wireless RALCWI Vocoder Evaluation Kit
- Digital Voice Innovations Documents
| ADM | Adaptive Delta Modulation. |
| CVSD | Continuously Variable Slope Delta Modulation: A method by which a voice signal is digitised for transmission, and then changed back to an analogue voice signal during reception. |
| dPMR | digital Private Mobile Radio. |
| FEC |
Forward Error Correction: A method of obtaining error control in data transmission in which the
source (transmitter) adds 'check bits' to the outgoing data stream;
the destination (receiver) recognises only the portion of the data that contains no apparent errors.
Because FEC does not require handshaking between the source and the destination, it can be used for the broadcasting of data to many destinations simultaneously from a single source. |
| LMR | Land Mobile Radio system. |
| PAN | Personal Area Network. |
| PCM | Pulse Code Modulation. |
| PMR | Private Mobile Radio. |
| RALCWI | Robust Advanced Low Complexity Waveform Interpolation: A low bit-rate algorithm for vocoder implementation; licensed to Spirit DSP. |
| TDD | Time Division Duplex. |
| TDMA | Time Division Multiple Access. |
| VAD | Voice Activity Detector (as described in the (CML) CMX6x8 series of datasheets). |
| Viterbi |
A dynamic programming algorithm that is used to decode a particular convolutional code.
This algorithm is used in the (CML) CMX6x8 series of vocoders. |
| Vocoder | Voice Encoder, Decoder: An electronic device or system for synthesising and digitising speech. |
| VoIP | Voice over Internet Protocol: a family of transmission technologies for voice communication over IP networks such as the Internet or other packet networks. |