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DIP Switch Functions
For troubleshooting purpose, user can conduct remote loopback and local loopback test. TC1720 also has
a built-in signal generator for user to validate fiber optic link. There are two groups of DIP switches: one
at the front panel, the other one is located at the center of the PC board.
Front Panel Switches
There are four DIP switches located at the front panel. Usually, they are very
useful during installation or troubleshooting. They are described as follows:
DIP #1:
Remote loop back. This switch (DIP #1) initiates the Remote loop
back function. The composite optic signal is received from optic "RxA"
and decoded, then looped back to optic "TxA."
DIP #2:
Local loop back (for diagnostic use). When DIP #2 is pressed down, an electrical signal loop
is created, the input electrical signal is converted to the TTL level and looped back.
DIP #3:
Internal clock generator "off" when DIP #3 is in the up(off) position. When switched to the down
("on") position, the received clock signal (from the remote side) is also used as an internal clock
signal and is transmitted to the user's equipment.
DIP #4:
Disable dry contact alarm.
These functions can be initiated from one of four DIP switches accessible from front panel. Under normal
operation, all the switches should be set in "UP" position.
SW1 Internal PCB Dip Switches
There are other eight DIP switches located at the PC board and can not be accessed from front panel. These
switches are usually only used during installation.
SW1-1:
Enable signal generators. This switch initiates the built-in Signal Generator function. The unit
will generate a visual signal to verify optic link.
SW1-2:
Configure TC1720's interface as a DCE or DTE. Off: DCE On: DTE
SW1-3:
Enable RxB. (On dual fiber optic models only)
SW1-4:
Async/Sync. Configure unit as Async or Sync. On: Async Off: Sync
Note: DIP Switches SW1-5 through SW1-8 are used for the internal clock generator. If the internal clock
from the TC1720 will be utilized, a clock rate can be selected according to the following table.
1
0
SW1-5:
x
SW1-6:
SW1-7:
SW1-8:
8k
Table 1. TC1720 Internal Clock Settings (Internal SW1)
3
5
7
2
4
6
x
x
x
x
x
x
x
x
x
x
x
9.6k
16k 19.2k 32k 38.4k 56k
For Oscillator: 8.192Mhz
8
9
10 11 12
13
x
x
x
x
x
x
x
x
x
x
64k
128k
256k
512k 1.024M
2.048M
-5-
(Optional Dual Optics)
User's Manual
1 2 3 4
1
RMTLB
LOCLB SLAVE-CLK
15
14
x
x
x
x
Legend:
x
x
x
This table shows the
Internal Clock speed
x
x
x
when the TC1720 is
DCE, on DB37 pin 5
& 23.
4.096M
5 - 10M
TC1720
Rev. 1.4
2
3
4
DIS ALM
Internal
DIP
Switches
(SW1)
X = ON
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