NRI—Technical description
NGT Transceiver System Technical Service Manual 267
NRI Vocoder PCB
The Vocoder is essential in the operation of the NRI. It is a small plug-in module that
contains a special-purpose voice coding integrated circuit. The function of this module is
to convert an incoming analog audio signal that represents voice, into a digitised
compressed data stream suitable for transmission through the digital modem link. It also
decodes an incoming digital data stream and reconstructs voice audio. Other components
present on this module are used to regulate supply rails and to provide interfacing to the
rest of the NRI unit. The vocoder interfaces to the microcontroller using an 8-bit parallel
interface.
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