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The Model 3010 requires no configuration prior to, or subsequent
to, installation: It is strictly "plug and play". This section tells how to
connect the Model 3010 to a modem and to three DTE devices and
how to operate the Model 3010.
3.1 INTERFACE PORTS
The Model 3010 has three DB-25 female DTE ports and one
DB-25 male modem port. Either
all
connected devices must be
asynchronous or they must
all
be synchronous: The Model 3010
performs no data conversion. The DTE ports are labeled DTE #1, DTE
#2 and DTE #3. The modem port is labeled MODEM. As figure 1
(below) illustrates, input port DTE #1 is on one end of the unit. DTE
ports DTE #2 and DTE #3 are
on top
when the Model 3010 is oriented
in a normal fashion.
3.1.1 DTE DEVICE CONNECTION
The Model 3010 lets three DTE devices contend for the opportunity
to transmit to one modem. The Model 3010 controls modem access by
monitoring the connected devices (DTE #1, DTE #2 and DTE #3) for
the presence of RTS. If two or three devices raise RTS simultaneously,
DTE #1 has priority over
both
DTE #2 and DTE #3. In the same way,
DTE #2 has priority over DTE #3.
Therefore, when connecting DTE devices to the Model 3010, use
the unit's prioritization scheme to your advantage. For example, if you
expect a particular device to monopolize access to the modem, that
device should be connected to DTE #3. This way, the other two
devices will have a better chance of being able to transmit.
3
4
Figure 1. Model 3010 showing port locations
DTE Cable Pin-outs
Each DTE device port on the Model 3010 is configured as a DCE
(i.e., it looks just like a modem port to the DTE device). Therefore, you
don't need to use any crossover cables. When connecting a DTE
device to the Model 3010, use a
straight through
RS-232 cable with a
length of 50 feet or less. Performance may degrade with longer
cables, especially at higher data rates.
3.1.2 MODEM CONNECTION
The Model 3010 is designed to plug directly into the female DB-25
port of an asynchronous or synchronous modem. If you must use a
cable to connect the Model 3010 to the modem, it should be a
straight
through
RS-232 cable. Note: Since the Model 3010 draws its
operating power from the modem interface, this cable should be 12
inches or less in length.
3.2 OPERATION
The Model 3010 always connects RS-232 pins 1,3,6,7,8-19 & 21-
25
straight through
from the modem to each DTE device. This allows
the modem to transmit in parallel to the DTE devices. The Model 3010
allows each DTE device to
contend
for the right to transmit to the
modem by raising RTS. When a DTE device has gained the right to
transmit, the pins shown below are then connected straight through to
the modem:
DTE Device
Modem
2 (TD) ------------------------------------------2 (RD)
4 (RTS) ----------------------------------------4 (RTS)
5 (CTS) ----------------------------------------5 (CTS)
20 (DTR) --------------------------------------20 (DTR)
The Model 3010 is transparent to data rate and protocol, requires
no configuration and requires no AC power or batteries for operation.
DTE #1
(DB-25 female)
DTE #2
(DB-25 female)
DTE #3
(DB-25 female)
MODEM
(DB-25 male)