The Use Of Voice Compression Through The Pstn; Echo Cancellation; Compliance Statement For Taiwan - Cisco 7920 Regulatory Compliance And Safety Information Manual

Unified wireless ip phone and peripherals

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The Use of Voice Compression through the PSTN

Because of the extensive delay already experienced when calling cellular and

international networks, some of which is already caused by their use of voice

compression technologies. Telecom Access Standards will only approve

G711 voice technology for use on the PSTN. G711 is an 'instantaneous

speech-encoding technique' whereas G729 and all its variants are considered

'near instantaneous' introducing additional delay into the speech signal.

Echo cancellers are not normally required in the Telecom PSTN because

geographic delays are acceptable where CPE return loss is maintained within

Telepermit limits. However, those private networks making use of

Voice-over-IP (VoIP) technology are required to provide echo cancellation

for all voice calls. The combined effect of audio/VoIP conversion delay and

IP routing delay can cause the echo cancellation time of 64 mS to be required.

This section contains the compliance statement for Taiwan.

Regulatory Compliance and Safety Information for Cisco Unified Wireless IP

Phone 7920 Series and Peripherals

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