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1 - SAGEM F@st™ 1000 modem overview
User Guide - N56815740110
No reproduction or communication without the written consent of SAGEM SA
Page 1-7
1.6 Bearer and transmission mode
1.6.1 ADSL
Asymmetric Digital Subscriber Line:
! The conventional telephone line is used to superimpose the transmission of high speed
digital signals on the conventional telephone signals.
! Transmission is said to be "asymmetric" because the maximum bit rate received by the user
can be up to ten times higher than the maximum bit rate employed by the user.
It is important to remember the following points:
! The real bit rates of your ADSL line will depend on the Quality of Service specified by your
Operator and by your Service Provider.
! The telephony and digital transmission services are totally independent and can be used at
the same time. In addition, the telephone service does not depend on the state of the
SAGEM F@st™ 1000: whether powered up or powered down, whether the data connection
is established or not, the telephone service will always be available.
1.6.2 ATM
ATM (Asynchronous Transfer Mode) is a transmission technique whereby the flow of data
(received in packets of variable length) is segmented into smaller packets of fixed length called
cells (53 octets long).
These cells are conveyed from end to end (through the network's various ATM elements) via
virtual channels.
Each virtual channel (VC) is defined by two identifiers supplied by the Operator:
! VPI (Virtual Path Identifier)
! VCI (Virtual Channel Identifier).