29
TERMINAL SERVERS
The RJ-45 adapter does not support chassis ground but does supply signal
ground to both pin 4 and pin 5. The reason for this is that on many DB25
devices, pin 1 is left unconnected. In other cases, signal ground and chassis
ground are not electrically equivalent and connecting one to the other with a
cross-cable can potentially damage
both
devices. The Transmit Return (pin 4)
and Receive Return (pin 5) pins must be connected to signal ground (pin 7
on the DB25) when connecting an RJ-45 connector to an RS-232 connector.
The RS-232 and RS-423 standards specify a maximum length of cable that
may be used to connect devices. For example, the RS-232 specification for
9600 baud connections limits the cable length to 50 feet. In practice, the
50-foot limit is often exceeded and this may cause noise that may also lead
to interference and unpredictable results. When cabling directly from a
Terminal Server to an RS-423 terminal, use twisted pair cabling for maxi-
mum noise immunity. Using long flat cables may result in noise problems.
3.3 Power On Procedure and Diagnostics
3.3.1 S
INGLE
-P
ORT
T
ERMINAL
S
ERVER
Once the unit is powered, the power LED turns ON and the device goes
through initial “Power On” diagnostic tests. During these tests, which last for
approximately three seconds, all the unit LEDs should alternate ON and then
OFF. If a hardware failure is detected during any test, one or more of the
LEDs will flash at a constant rate. If this happens, call for technical support.
The PWR LED always remains ON when connected to power.
3.3.2 4-
AND
8-P
ORT
T
ERMINAL
S
ERVERS
Immediately after the Terminal Server is powered on, it executes a “Power
On” diagnostic procedure and all of the LEDs on the front panel will flash. All
the LEDs light sequentially from left to right for approximately five seconds.
After the last LED has gone out, only the Power LED should remain on. The
entire diagnostic procedure lasts for approximately ten seconds. Normal
operation of the Terminal Server can commence once these diagnostics
complete successfully.\
If a diagnostic test reveals a fatal error, then all of the LEDs will light for a
few seconds. An error code will be indicated by leaving some of the port LEDs
ON. The display will then alternate between having all the LEDs on and the
error-code display. In the unlikely event of failure, contact technical support
for further assistance. If the diagnostic test reveals a non-fatal error (such as
the failure of a particular port), the Terminal Server will continue to operate.
Summary of Contents for LE2101A-BT-R2
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