4.1.1 Two-Wire Cable Connection Via RJ-45
A. The RJ-45 jack on a Model 1080A Series Short Range Modem is
prewired for a standard TELCO wiring environment. To be sure you
have the right wiring, use the table below as a guide.
RJ-45 SIGNAL
1 -------------NC
2 -------------GND†
3 -------------RCV
4 -------------XMT
5 -------------XMT
6 -------------RCV
7 -------------GND
8 -------------NC
†Connection to ground is optional
B. Proper wiring of pairs between the two modems is as follows:
SIGNAL PIN# COLOR* COLOR PIN# SIGNAL
XMT 4 Green------------Green 4 XMT
XMT 5 Red---------------Red 5 XMT
*Standard color codes—yours may be different
C. AT&T standard modular color codes:
13
1 - Blue
2 - Orange
3 - Black
4 - Red
5 - Green
6 - Yellow
7 - Brown
8 - Slate
4.1.2 Two-Wire Cable Connection Via Terminal Blocks
If you are not going to use the modular jacks, follow the
instructions below.
A. Locate the terminal block on the back of the unit. It should
look like the following diagram:
NOTE: * The “+” and “-” indicators are for reference only. The Model 1080A Series is
not sensitive to polarity.
B. Connect one wire of the pair to a Transmit lug (TX+ or TX-) on
both the local and remote Model 1080A or 1080A-64.
C. Connect the other wire of the pair to the other Transmit lug on
both the local and remote Model 1080A or 1080A/64.
D. If there is a shield around the telephone cable, it may be
connected to GND on the terminal block. We recommend connecting
the shield at the computer end only to avoid ground loops. A ground
wire is not necessary for proper operation of these units.
E. When you finish connecting the telephone line to units at both
ends, it should look like the following diagram:
4.2 FOUR-WIRE INSTALLATION
When communicating over a two twisted pair circuit, the Model
Series can operate full or half duplex, point-to-point or multipoint. In
two pair point-to-point applications, you will need a
pair
of Model
1080As or 1080A-64s for each circuit—one at
each end
of the single
pair wire. In two pair multipoint applications you will need three or more
Model 1080A Series units.. These can be connected using a star
topology, although a daisy chain topology is usually used.
14
RX+ RX- GND TX- TX+
XMT XMT
XMT XMT
GND GND
To Shield (Optional)
}One Pair