Voice Coding; 136; Pstn Call Setup Signaling - ZyXEL Communications ADSL VoIP IAD with 802.11g Wireless 2602HW Series User Manual

Prestige 2602HW Series User's Guide

9.5 Voice Coding

A codec (coder/decoder) codes analog voice signals into digital signals and decodes the digital
signals back into voice signals. The Prestige supports the following codecs.
9.5.1 G.711
G.711 is a Pulse Code Modulation (PCM) waveform codec. G.711 provides very good sound
quality but requires 64kbps of bandwidth.
9.5.2 G.729
G.729 is an Analysis-by-Synthesis (AbS) hybrid waveform codec that uses a filter based on
information about how the human vocal tract produces sounds. G.729 provides good sound
quality and reduces the required bandwidth to 8kbps.

9.6 PSTN Call Setup Signaling

Dual-Tone MultiFrequency (DTMF) signaling uses pairs of frequencies (one lower frequency
and one higher frequency) to set up calls. It is also known as Touch Tone®. Each of the keys
on a DTMF telephone corresponds to a different pair of frequencies.
Pulse dialing sends a series of clicks to the local phone office in order to dial numbers.
1. The Prestige does not support pulse dialing at the time of writing.

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Chapter 9 Introduction to VoIP