2.0 Specifications
Electrical: Half-duplex RS-485, two-wire
Fiber Interface: Optimized for 62.5/125 micron fiber cable
Wavelength: 850 nm
Speed: 0-1 MHz
Power Budget: 12 dB (with 62.5/125 micron fiber)
Distance: Fiber 2 km (distances can exceed 2 km depending on fiber loss)
RS-485: Per RS-485 specification
Connectors: Fiber (ST), RS-485 (DB-25 Female)
Power: 115 VAC/60 Hz (220 VAC/50 Hz optional)
Size: 3.5" L x 2" W x .875" H
Environment: 0 to 50 deg
C
, 5 to 95% RH (no condensation)
3.0 Installation
3.1 RS-485
The RS-485 connector to the Model 276A allows for half-duplex operation through a DB-25
female connector. Refer to the following chart for pin assignments.
DB-25F
Data Direction
2
Data I/O –
14
Data I/O +
7
Signal Ground
3.2 Fiber
The fiber optic end has been optimized for operation with 62.5/125-micron cable and comes
equipped with ST-type fiber optic connectors.
4.0 Operation
The Model 276A can be connected to any RS-485 device running at speeds up to 1 MHz. To
connect the units, the connections "Data I/O-" and "Data I/O+" are connected to the two-wire
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data from the RS-485 equipment. Pin 7 is Logic Ground (if the customer's equipment
requires it). To connect the 276A to another 276A, the fiber connector marked "T" should be
connected to the far-end fiber connector marked "R" and the local "R" should be connected
to the far-end "T."
In addition, power can be applied to the Model 276A by using Pin 9 on the DB-25 female
connector and Pin 7 as the ground connection. When using this pin, the input voltage should
be +12 VDC.
6.0 Hel
