TC1720
(Optional Dual Optics)
User's Manual
Rev. 1.4
-16-
Remote Electrical Loopback Test
1.
Set up the bench test as illustrated in Figure 9 below. Make sure all front panel SW2 dip switches on both
the Local & Remote TC1720's are to the up "Off" position.
2.
Connect four copper-wire jumpers to short (loopback) the DB37 Male connector on the rear of the
remote unit as follows (these copper-wire connections will loopback the signal at the remote TC1720):
3.
Set the BERT test set to the same (or as close to the same) data rate as the application you plan to connect
to (typically 19.2Kbps through 128Kbps Synchronous).
4.
The data bits should be selected as ‘8 bits’ and the data pattern should be set to ‘2047’ on the BERT
tester.
5.
At this point, the tester should indicate a Synchronous signal being received (if the optical cable and
connectors are good and the electrical cable has been connected properly).
6.
Verify that the "TxD," "RxD," "TxClk," "RxClk," "RxA," "PWRA or PWRB," and "Vcc" LEDs are solidly
lit on both the Local and Remote TC1720s. Note, the "ALARM" LED will be "Off" since there are optical
fiber cables connected. All other LEDs should be off.
You should not see any bit errors. To verify this, inject an error using the BERT tester to see if it will
be recorded by the tester, then verify that no additional errors appear after the user injected error.
Pin 4 (+SD) to Pin 6 (+RD)
Pin 22 (-SD) to Pin 24 (-RD)
Pin 17 (+TT) to Pin 8 (+RT)
Pin 35 (-TT) to Pin 26 (-RT)
Figure 9. Remote Electrical Loopback Test Connection Diagram
ALARM
ALARM
BERT Test Set
with RS-422/449
Local
unit
Remote
unit
RS-422/449
RS-422/449
ASYNC/SYNC
FIBER OPTIC MODEM
ASYNC/SYNC
FIBER OPTIC MODEM
TxB
TxB
TxA
TxA
RxB
RxB
(Optical redundant
models only)
DB37 Female
Cable
OPTIC
OPTIC
OPTIC
OPTIC
(Optional)
P
in
4
(S
D
)
to
P
in
6
(R
D
)
P
in
2
2
(S
D
)
to
P
in
2
4
(R
D
)
P
in
1
7
(T
T
) t
o
P
in
8
(
R
T)
P
in
3
5
(T
T
) t
o
P
in
2
6
(R
T
)
(Optional)
RxA
RxA
PWR
A
PWR
A
PWR
B
PWR
B
DC Power Supply
12VDC@ 500mA
DC Power Supply
12VDC@ 500mA
Male DB37
Male DB37
