Patton electronic 2710 - Manual (Page 17)

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both synchronize the terminal equipment and to identify the signal-
ing frames.” (Sec. 4.1.1)
ESF: This stands for Extended Superframe Format, a line format
developed by AT&T. AT&T Technical Reference 54016 (TR 54016)
deÞnes the ESF, a format which is commonly used to allow monitor-
ing of the network interface performance over the Facility Data Link
(FDL). AT&T TR 62411 says, “the Extended Superframe Format
“extends” the DS1 superframe structure from 12 to 24 frames…for a
total of 4632 bits. It redeÞnes the 8 kb/s channel previously used
exclusively for terminal and robbed bit signaling synchronization.”
The ESF provides a 4 kb/s data link, called the FDL, which allows for
in-service monitoring and fast troubleshooting. Certain network ser-
vices require the ESF.
UNFRAMED: This is a special mode that allows you to achieve the
maximum possible data rate of 1.544 Mb/s (million bits per second)
by using the framing bits for data transmission. There is no signaling
or FDL. This is commonly used for campus connections, and by the
Federal government and the military. This format is not to be used
when connecting to a public carrier’s network without its permission.
This provides one channel at a rate of 1.544 Mb/s. In addition, this
format can be used with external clocking.
– Line Coding: B8ZS (default)
Options: AMI, B8ZS, B7ZS.
AMI: Alternate Mark Inversion deÞnes a pulse as a “mark”, a binary
one, as opposed to a zero. In a T1 (DS1) network connection, sig-
nals are transmitted as a sequence of ones and zeros. Ones are
sent as pulses, and zeros are sent as spaces, i.e., no pulse. Every
other pulse is inverted from the previous pulse in polarity, so that the
signal can be effectively transmitted. This means, however, that a
long sequence of zeros in the data stream will cause problems,
since the CSU/DSU receiving the signal relies on the signal to
recover the 1.544 Mb/s clock. To get around this problem, one
method is to limit the data rate per channel (known as a DS0,
because it is a 64 kb/s portion of the DS1 frame or superframe) to
56 kb/s and forcing a pulse in the last data bit to ensure a minimum
pulse density in the signal. If you must use AMI with a DS0 data rate
of 64 kb/s, you should ensure that the data terminal equipment con-
nected to the unit provides a minimally acceptable pulse density. For
this reason, there are advantages to using B8ZS instead.