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Chapter 2 - What is in the Box 15
Cyclades-PR4000
Provisioning the T1/E1 Dialup Lines
This section provides information useful when provisioning the T1 or E1 dialup trunk lines for use with the Cyclades-
PR4000 Remote Access Server. Line provisioning parameters vary widely depending on the switch being used at
the central office and the service options offered by the carrier. In North America and Japan, a digital trunk uses
a T1 speed of 1.5Mbps. In Europe and most other countries, a digital trunk runs at E1 speeds of 2Mbps. A digital
trunk is a Time Division Multiplexed (TDM) line that carries information from several channels in digital form. In a
given country, only E1 or T1 is offered.
Signaling: ISDN-PRI (CCS) or CAS
Phone lines carry signaling information used to establish and maintain connections. In a regular phone this
information translates into dialing, ring, busy signal, dial tone, caller ID, etc. In an analog phone line, the signaling
information shares the channel used to carry voice. In a T1 or E1 trunk, the signaling information for the trunk can
be carried by a separate channel or can share the same channel used to carry data. There are three basic
signaling protocols: ISDN-PRI (T1 or E1), CAS-BR (T1), or R2D/MFR2 (E1).
Newer systems use the ISDN-PRI signaling protocol, with channels dedicated to control. With this protocol, a T1
line carries 23 phone connections and an E1 line carries 30 phone connections.
In North America, older T1 systems use CAS (Channel Associated Signaling) protocols. These protocols “steal”
some of the bandwidth from the data channels using a scheme called “bit robbing” (BR) and allow a T1 line to
carry 24 phone connections. In other countries, older E1 systems use R2D/MFR2 signaling with a dedicated
channel, leaving 30 phone connections. Lines with CAS or R2D/MFR2 signaling are sometimes referred as
“Channelized T1/E1” or “DS-1”.
ISDN-PRI provides more control over connections than the older CAS or R2Ds. Given a choice between ISDN-
PRI and CAS/R2D, select ISDN-PRI.
Number of Phone Lines
In most applications, the maximum number of phone lines (for the protocol used) are purchased. However, it is
also possible to request fewer lines. When using fewer lines, make sure to disable the remaining channels using
the menu CONFIG =>INTERFACE =>E1/T1 =><CHANNEL> =>ENCAPSULATION =>INACTIVATE.