User's Manual

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OL-19076-01
assurance that any item will work correctly in all respects with another item
of Telepermitted equipment of a different make or model, nor does it imply
that any product is compatible with all of Telecom's network services.
Use of IP Networks with the PSTN
Internet Protocol (IP) by its nature introduces delay into speech signals as
each data packet is formulated and addressed. Telecom Access Standards
recommends that suppliers, designers and installers using this technology for
calls to or from the PSTN refer to ITU E Model requirements in the design of
their networks. The overall aim is to minimise delay, distortion and other
transmission impairments, particularly for those calls involving cellular and
international networks, which already suffer extensive delay.
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.