Telepermitted equipment of a different make or model, nor does it imply that any
product is compatible with all of Telecom's network services.
The Use of IP Networks through the PSTN
R 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 minimize delay, distortion and other
transmission impairments, particularly for those calls involving cellular and
international networks, which already suffer extensive delay.
R Echo cancelers 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
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 ³ 64 ms to be required.