Cisco TelePresence Server 7010, Hardware Installation And Maintenance Manual

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Preparing for Installation 2-39
Preparing Network Connections
•
X.21: DTE mode with DB-15 plug; DCE mode with DB-15 receptacle
•
EIA-530: DTE mode with DB-25 plug
E1-G.703/G.704 Cables
Figure 2-31, Figure 2-32, and Figure 2-33 show the unbalanced and balanced cables used for
connection between the E1-G.703/G.704 port adapter and your network. The port-adapter end of
each cable has a DB-15 connector.
Figure 2-31 E1-G.703/G.704 Interface Cable for 75-Ohm, Unbalanced Connections
(with BNC Connectors and Coaxial Cables)
Figure 2-32 E1-G.703/G.704 Interface Cable for 120-Ohm, Balanced Connections
(with DB-15 Connectors on Both Ends)
Figure 2-33 E1-G.703/G.704 Interface Cable for 120-Ohm, Balanced Connections
(with Twinax Connectors and Cables)
Caution
It is a requirement of the statutory approval of the E1-G.703/G.704 interface that the
jackscrews on the DB-15 connector backshell are securely screwed down while the FSIP is
operating.
NRZ and NRZI Formats
All data communications interfaces support both nonreturn to zero (NRZ) and nonreturn to zero
inverted (NRZI) formats. Both formats use two different voltage levels for transmission. NRZ
signals maintain constant voltage levels with no signal transitions (no return to a zero voltage level)
during a bit interval and are decoded using absolute values (0 and 1). NRZI uses the same constant
signal levels but interprets the presence of data at the beginning of a bit interval as a signal transition
and the absence of data as no transition. NRZI uses differential encoding to decode signals, rather
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