4.1.3 Connecting the Twisted Pair (120 ohm) to the G.703
Network
The Model 2701 is equipped with a single RJ-48C jack for connec-
tions to a 120 ohm twisted pair G.703/G.704 network interface. If your
G.703/G.704 network terminates via RJ-48C, use the connection dia-
gram (Figure 4) following the pinout and signals chart below to connect
the 120 ohm G.703/G.704 network channel.
RJ-45 Cable (8-Wire)
G.703/G.704
2701
NETWORK SIGNAL
SIGNAL
PIN#
RX+
1-----------------------TX+
RX-
2-----------------------TX-
TX+
5-----------------------RX+
TX-
4-----------------------RX
Shield
3-----------------------Shield
Shield
6-----------------------Shield
11
4.2 Connecting the Serial Port
The Model 2701/B, C, D supports RS-530, V.35, X.21 serial port
connections. This section describes how to connect the serial ports to
your terminal equipment.
4.2.1 Connecting to a “DTE” Device
The serial port on the 2701/B (RS-530 version) and 2701/C (V.35
version) is hard-wired as a DCE. Therefore these modules “want” to
plug into a DTE such as a terminal, PC or host. When making the
connection to your DTE device, use a straight through cable of the
shortest possible length—we recommend 6 feet or less. When pur-
chasing or constructing an interface cable, please refer to the pin dia-
grams in Appendix D as a guide.
4.2.2 Connecting to a “DCE” Device
If the Model 2701 serial interface is hard-wired as a DCE (all
except the X.21 version), you must use a
null modem cable when con-
necting to a modem, multiplexer or other DCE device. This cable
should be of the shortest possible length—we recommend 6 feet or
less.
4.2.3 Configuring the X.21 Interface (2701/D)
The serial port on the X.21 interface is default wired as a DCE, but
may be switched to a DTE. This is done by reversing the orientation of
the DCE/DTE strap, as described below:
To reverse DCE/DTE orientation, remove the top case. Refer to
section 4.1.2.
The DCE/DTE strap is located near the DB15 connector on the
top side of the board. The arrows on the top of the strap indicate the
configuration of the X.21 port (for example, if the DCE arrows are
pointing toward the DB-15 connector, the X.21 port is wired as a DCE).
Reverse the DCE/DTE orientation by pulling the strap out of its socket,
rotating it 180º, then plugging the strap back into the socket. You will
see that the DCE/DTE arrows now point in the opposite directions,
showing the new configuration of the X.21 port.
NOTE: If the 2701/D is configured as a DTE, the clocking mode
must be set for external clock.
12
(No Connection) 8
(No Connection) 7
(No Connection) 6
(TX+) 5
(TX-) 4
(No Connection) 3
(RX-) 2
(RX+) 1
8
7
6
5
4
3
2
1
Figure 4: G.703/G.704 170 Ohm Connection.
