Sel 411L - Figure 3.181 CCITT G.703 Typical Connection; Figure 3.182 Back-To-Back CCITT G.703 Connection; Table 3.138 CCITT G.703 Cables

P.3.267
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Communication and Timing
CCITT G.703
Codirectional
Interface
G.703 is an industry standard which describes an electrical interface for
transmitting voice or data over a digital circuit. The codirectional version uses
two balanced pairs, one for transmission and one for reception. No clock
polarity selections are necessary because the synchronizing clock is embedded
within the transmit and receive data streams. The G.703 interface is
transformer isolated from the chassis to 1500 V rms. Since each differential
pair is transformer isolated, there is no signal common. To prevent ground
loops, ground the cable shield only at the multiplexer. Refer to Table 3.138 for
the G.703 cable appropriate to your application. All of those cables connect
the shield at the multiplexer end only.
The DB-25 connector pinout on the relay and the direction of signal flow is
shown in Figure 3.181.
Figure 3.181 CCITT G.703 Typical Connection
Back-to-Back Connections
Figure 3.182 shows an example of two relays, connected back-to-back,
configured for G.703 protocol. The G.703 protocol in the relay does not
require the use of an external multiplexer, such as an SEL-3094, to provide a
timing source for data transfer.
Figure 3.182 Back-to-Back CCITT G.703 Connection
IEEE Standard C37.94
Fiber-Optic Interface
IEEE Standard C37.94 defines a direct relay-to-multiplexer interface over
multimode fiber-optic cable. This prevents problems associated with electrical
interfaces and provides excellent noise immunity.
The standard defines the data structure and encoding, and also defines the
physical interface (ST connector, 850 nm light wavelength, 50 or 62 micron
multimode fiber) ensuring that all C37.94 compliant relays interface with all
C37.94 compliant multiplexers.
Table 3.138 CCITT G.703 Cables
Manufacturer Product Channel Card
Interface
Adapter
SEL Cable
SEL SEL-3094 NA Interface
adapter
C461
RFL IMUX DS561 MA408IA C452
TXDA
TXDB
RXDA
RXDB
SHIELD*
2
14
3
16
Relay
CH1/2
DB25 pin male
MUX
or Interface
Convertor
Relay (2)
2 TXDA
14 TXDB
3 RXDA
16 RXDB
Relay (1)
TXDA 2
TXDB 14
RXDA 3
RXDB 16