Rs422 Interface - GE t60 Instruction Manual

3 HARDWARE
e) TEST MODES (SWITCHES S5 AND S6)
MINIMUM REMOTE LOOPBACK MODE:
In Minimum Remote Loopback mode, the multiplexer is enabled to return the data from the external interface without any
processing to assist in diagnosing G.703 Line Side problems irrespective of clock rate. Data enters from the G.703 inputs,
passes through the data stabilization latch which also restores the proper signal polarity, passes through the multiplexer
and then returns to the transmitter. The Differential Received Data is processed and passed to the G.703 Transmitter mod-
ule after which point the data is discarded. The G.703 Receiver module is fully functional and continues to process data and
passes it to the Differential Manchester Transmitter module. Since timing is returned as it is received, the timing source is
expected to be from the G.703 line side of the interface.
DUAL LOOPBACK MODE:
In Dual Loopback Mode, the multiplexers are active and the functions of the circuit are divided into two with each Receiver/
Transmitter pair linked together to deconstruct and then reconstruct their respective signals. Differential Manchester data
enters the Differential Manchester Receiver module and then is returned to the Differential Manchester Transmitter module.
Likewise, G.703 data enters the G.703 Receiver module and is passed through to the G.703 Transmitter module to be
returned as G.703 data. Because of the complete split in the communications path and because, in each case, the clocks
are extracted and reconstructed with the outgoing data, in this mode there must be two independent sources of timing. One
source lies on the G.703 line side of the interface while the other lies on the Differential Manchester side of the interface.
a) DESCRIPTION
The following figure shows the RS422 2-Terminal interface configuration at 64K baud. AWG 22 twisted shielded pair is rec-
ommended for external connections. This interface module is protected by surge suppression devices which optically iso-
lated.
SHIELD TERMINATION
The shield pins (6a and 7b) are internally connected to the ground pin (8a). Proper shield termination is as follows:
Site 1: Terminate shield to pins 6a and/or 7b; Site 2: Terminate shield to 'COM' pin 2b.
GE Multilin
DMR G7X
DMX G7R
DMR G7X
DMX G7R
T60 Transformer Management Relay
3.3 DIRECT I/O COMMUNICATIONS
DMR = Differential Manchester Receiver
DMX = Differential Manchester Transmitter
G7X = G.703 Transmitter
G7R = G.703 Receiver
DMR = Differential Manchester Receiver
DMX = Differential Manchester Transmitter
G7X = G.703 Transmitter
G7R = G.703 Receiver

3.3.5 RS422 INTERFACE

3
3-25