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USER’S MANUAL
Control Leads
There are a number of “control leads” defined in the V.35 and X.21 standards.
CSU/DSUs will frequently have indicator lights showing the status of these signals,
which may be useful when troubleshooting problems.
In the direction Zephyr Xstream - > TA/CSU, the Xstream provides DTR (Data
Terminal Ready) and RTS (Request to Send). Both of these signals are made active
when the V.35 interface is selected and the Zephyr Xstream is ready for operation.
HOT TIP!
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Since the data is generally clocked from the master clock at the Telco anyway,
handshaking is unnecessary. Timing variations between the various handshake
signals varies and may cause equipment incompatibilities. If this occurs, it is entirely
ok to disable handshake signals on the CSU/DSU using the appropriate DIP switch or
command.
In the direction CSU/DSU - > Zephyr Xstream, only CD (Carrier Detect))is
implemented. This signal is used to tell the Zephyr Xstream which port/channel has
been connected and activated. It is used for internal selection of the network clock
source. When the TEL menu selection Interface is set to “V.35” the TEL status screen
will indicate “Inactive” or “Active” depending on whether the CD signal is present
for that channel.
Configuring CSU/DSUs
There will generally be at least two main configuration menus. One for interface to
the DTE (Data Terminal Equipment) and one for the interface to the “loop” or
“line”. Your CSU/DSU manual (or manufacturer) should have information on the
correct settings for the various options.
DTE Options:
Set to “Synchronous” and set the bit rate to match the Zephyr Xstream’s and line’s
bit rate (usually 56kbps). If necessary, you may disable any handshaking signals by
setting them to “forced” or “ignored” since handshaking is not required with
synchronous data. “Anti streaming” or “scrambling” options should be disabled.
Loop or Line Options:
Set to the speed of your line (usually either 56 or 64kbps). The Xstream’s CODEC
menu option Bit Rate must be set to the same rate as the line. Your Telco or
CSU/DSU manual should be able to give you the correct setting for any other
options.
Clock Options:
It is essential that the clock option be set to “network” or “from loop”. The Xstream
will clock its synchronous data to the clock from the CSU/DSU. In order to prevent
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Section 8 The V.35/X.21 INTERFACE OPTION