GE D90 Plus Instruction Manual page 73

CHAPTER 3: INSTALLATION
G.703 communication interface
NOTE:
RS422 communication interface
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
AWG 24 twisted shielded pair is recommended for external connections, with the shield
grounded only at one end. Connecting the shield to pin B1a or B8a grounds the shield since
these pins are internally connected to ground. Thus, if pin B1a or B8a is used, do not
ground at the other end. The G.703 module chassis is protected by surge suppression
devices.
The following figure shows the 64 kbps ITU G.703 co-directional interface configuration.
Figure 32: G.703 module connections
The G.703 octet timing and timing mode are set using the
The following figure shows the typical pin interconnection between two G.703 interfaces.
All pin interconnections are to be maintained for a connection to a multiplexer.
Figure 33: Typical pin interconnection between two G.703 interfaces
Pin nomenclature may differ from one manufacturer to another. Therefore, it is not
uncommon to see pinouts numbered TxA, TxB, RxA and RxB. In such cases, it can be
assumed that "A" is equivalent to "+" and "B" is equivalent to "–".
The RS422 inter-relay communications module is a dual-channel dual-clock RS422
interface. The module can be configured to run at 64 or 128 kbps. AWG 24 twisted shielded
pair cable is recommended for external connections. The module is protected by an
optically-isolated surge suppression device.
The two-channel two-clock RS422 interface is intended for use with two independent
channel banks with two independent clocks. It is intended for situations where a single
clock for both channels is not acceptable.
The shield pins (B1a and B8a) are internally connected to chassis ground. Proper shield
termination is as follows:
• Site 1: terminate shield to pins B1a.
• Site 2: connect COM pin B1b to site 1 COM pin B1b. Note that pins B1b and B8b are
internally connected.
The clock terminating impedance should match the impedance of the line.
ELECTRICAL INSTALLATION
setting.
Protocol Encoding
63