Product Manual - DM991 Series V Family - 204.4092.08
25
5.
G.703 - G.704 INTERFACE
The interface allows usage of coaxial cable (75ohms) or for twisted pairs (120ohms). The cables are
attached through transformers, so there is no polarity for the twisted pair.
5.1. DM991S/SE
There are straps which allow connecting the external net of the coaxial cable to the ground cable. This
works either for the input channel (RX-IN) as for the output channel (TX-OUT).
The output wire that goes through pin 18B of the EDGE 2x30 connector is connected to the central pin of
the E10 strap, and is the TX-OUT cable, that can be connected to the ground cable through this strap. In
this case, it must be identified for each cabinet model which was the TX-OUT screw to be grounded by the
strap, so it can be connected to the coaxial cable net. On the sub-racks, usually, the inferior TX-OUT
screw is grounded.
The input wire that goes through pin 21B of the EDGE 2x30 connector is connected to the central pin
through strap E11, and is the RX-IN cable, that can be connected to the ground wire through this strap.
The same identification procedure of which screw has been grounded must take effect in this case. In the
sub-rack, usually, the inferior TX-OUT screw is grounded.
Modem signal G.703 is available on Dial Backup terminals in the terminal strip.
Function
Signal
screw connector
block
Signal source
Received data
OUT core
BkpC
DM991
Received data
OUT shield
BkpD
DM991
Transmitted data
IN core
BkpA
E1 Network
Transmitted data
IN shield
BkpB
E1 Network
Table 12. DM991S/SE - Pinout in the G.703 Screw connector block.
Function
Signal
DB25
Signal source
Received data
OUT core
4
DM991
Received data
OUT shield
17
DM991
Transmitted data
IN core
2
E1 Network
Transmitted data
IN shield
15
E1 Network
Table 13. DM991S/SE - G.703 Telebrás (DB25) Standard Pinout
When using twisted pair (120ohms), make sure the straps are not in the ground position.
When installing the DM991S/SE, remove the protection varistors from the cabinet or sub rack. These
varistors deform the G.703 signal pulses, which can cause wrong bits, working intermittently, or even
completely stopping the circuit activation. In case the cabinet or shelf was made by DATACOM or has
gas-filled valve arrester instead of varistors, no changes are required.
Summary of Contents for DM991C
Page 1: ...DM991 SERIES V DM991C DM991CE DM991S DM991SE PRODUCT MANUAL 204 4092 08 rev 08 Date 8 12 2008 ...
Page 66: ...Product Manual DM991 Series V Family 204 4092 08 66 Figure 31 LDL Test Converter Mode ...
Page 89: ...Phone 55 51 3358 0100 Support 55 51 3358 0122 Fax 55 51 3358 0101 www datacom ind br ...
