CML - Digital Voice
CML's DuraTALK family of digital voice products comprises a range of flexible technologies supporting voice-data generation, coding, transcoding and decoding functions for digital communication systems, as well as many other in-band audio applications where there is a need for storage and playback.
The DuraTALK family currently consists of the following technologies:
TWELP™: Crystal clear digital voice for professional radio
RALCWI™: CML's low bit-rate Vocoder
Transcoding: On-chip multi-transcoding/conversion of data formats (Linear PCM, G.711, G.723.1, G.729A, CVSD)
CVSD and ADM: Flexible error tolerant encoders/decoders
The flexible, low power, highly integrated TWELP, RALCWI, Transcoder and CVSD ICs are suited to wireless and wireline voice applications such as voice scramblers, alarm systems, military field applications and professional or leisure digital two-way radios.
TWELP™ 'Tri-Wave Excited Linear Prediction' is a new state-of-the-art voice coding system, designed to meet the needs of the demanding digital wireless narrowband radio systems. TWELP™ technology provides the highest quality natural sounding voice, at equivalent bit-rates, as well as good reproduction of non-voiced signals such as: police, fire and ambu-lance sirens. TWELP™ is also extremely tolerant to acoustic noise and includes an advanced noise reduction system to suppress background noise. Supporting the voice coding function is a robust forward error correction (FEC) scheme, an important feature to mitigate errors inherent when transmitting over narrowband radio channels in challenging conditions.
RALCWI™ 'Robust Advanced Low-Complexity Waveform-Interpolation' based ICs provide near-toll-quality voice performance at very low bit rates. RALCWI technology uses proprietary signal-decomposition and parameter-encoding methods, ensuring superior speech quality at high compression rates. RALCWI™ is a low bit rate vocoder technology that facilitates the transmission and reception of highly compressed voice over inherently noisy narrowband radio channels. In this area, RALCWI™ is positioned to address the high quantity/low cost, digital PMR/LMR markets.
ICs capable of converting analogue voice frequencies into one of several data formats (see the trancoder table, above) and/or the reverse. Facilitates the conversion from one data format to another and/or to an analogue format. (Linear PCM, G.711, G.723.1, G.729A, CVSD)
CML's CVSD 'Continuously Variable Slope Delta Modulation' products offer a flexible compand algorithm with programmable sampling clocks, data rates and force-idle operation.
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.