Digital Voice Systems VC-20-ATC-10B Dokumentacja Pobierz pdf (Strona 67)

FAA20 Embedded NEXCOM Vocoder

Board Manual

This manual has been prepared for the Federal Aviation Administration.

FA100-00107 (March 2004) – Rev 1.0.0 Page 61

8.3.1 ADAPT

The ADAPT command enables/disables the PCM rate adapter for truncated

timing mode. The adapter is never enabled in normal timing mode.

Table 11: ADAPT Command Syntax

ATTRIBUTE DESCRIPTION

SYNTAX ADAPT [onstate]

PARAMETERS onstate ON Enables rate adapter during truncated timing mode.

OFF Disables rate adapter during truncated timing mode.

FLASH YES

Request the current setting

COM1: adapt

> ADAPT OFF

EXAMPLES

Enable the rate adapter

COM1: adapt on

> ADAPT ON

The rate adapter sits in the path between the PCM interface and the linear

mixer. It allows the PCM interface to continue to operate at the nominal

sample rate (8 ksps) while the FAA20 is in truncated timing mode. When

enabled and truncated timing is activated, the audio is converted from the 8

ksps rate to the truncated timing rate of 6.67 ksps, i.e. the sample rate is

adjusted by 5/6. The rate adaptation is achieved through the use of an

interpolating multi-rate filter followed by a decimator. The rate adapter is

only available in truncated timing mode. See Section 5.3.4 for additional

details.

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Digital Voice Systems VC-20-ATC-10B Dokumentacja Strona 67