TC1720
(Optional Dual Optics)
User's Manual
Rev. 1.4
-7-
Optical Redundancy (optional)
If optic redundancy was ordered with the unit, figure below applies to its operation. Optic redundancy is used
to prevent the loss of data transmission in the event an optic cable, transmitter, or receiver is broken or
degraded. Should this occur, the secondary optic link & receiver "B" is enabled automatically, thereby
preserving the integrity of the communication. In the meantime, the "Alarm" LED will flash and the buzzer
will sound to indicate a cable breakage.
When the unit is equipped with optic redundancy,
the optic transmitter "TxA" and "TxB" both
transmit the same signal to the remote unit. It is
up to the remote unit to decide whether "RxA" or
"RxB" should be used as the valid incoming optic
signal. By default, "RxA" is the primary re-
ceiver; "RxB" is the stand by backup.
Figure 4. TC1720's Rear Panel
Dry Contact Alarm Relay
A terminal block connector at the rear panel
provides for the Dry Contact Alarm Relay. Nor-
mally in the OPEN position, any alarm condition
will force the switch to a CLOSED position. This
relay can be used in conjunction with an external
device to signal an alarm condition.
Power Supply and Rear Panel
The TC1720 consumes very low power. The standard input voltage is from 12VDC and current is 500mA
(max). You may use an external power adapter with the following specifications: 12V DC @800mA (positive
polarity at the left terminal when viewed from the rear panel).
The power plug can be connected into either power jack on the rear panel. Because the TC1720 is equipped
with a built-in power redundancy feature, the "POWER A" or "POWER B" LEDs on the front panel will
illuminate according to which power source the unit is drawing from. If power redundancy is utilized, both
LEDs will light.
For units with the -48V DC power supply option, a DC-to-DC converter is installed inside the unit. The DC
current requirement for the optional -48V DC power supply is @50mA.
RxA
Rx
RxB
Optic Signal
Detector
&
Automatic
Switchover
Control
TxA
Tx
TxB
TC1720
TxA
Tx
RxA
Rx
TxB
RxB
Optic Signal
Detector &
Auto Switch Over
Control
TC1720
TC1720
ALARM
RS-449
1
19
20
37
PWR
A
PWR
B
+ -
+ -
Terminal Block Connectors
for Power Supply "A" & "B"
DB37 Male
Connector
Dry Contact Alarm
Relay Connector
24VDC
12VDC
125VDC
48VDC
