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If you have a special application, we may already have a solution for you.
Give Ron a Call at 513-874-4796 or 513-638-0228 for additional information.
F485CT: Duplex Multimode Fiber to RS485 2 Wire Half Duplex Serial Converter


F485CT in Box

F485CT Label

"Let me spin a very large
RS485 network for you!"


Product Features

  • This unit features bi-directional serial conversion from 2 wire RS485 to a pair of ST 62.5 micron multimode ports.

  • Capable of extending the range of a RS485 communications link to 1Km minimum, typically 1mile.

  • The inherent noise immunity of the fiber cable allows reliable communications in environments that are hostile to other methods.

  • Optimized for non-isolated office/indoor point to point or multi-drop systems.

  • Transparent to all asynchronous data, with any combination of data, parity, and stop bits, at data rates up to 1Mbps. Faster speeds are available, in this, and our other products. No Jumpers or settings ordinarily required.

  • Fast auto turn-around, from transmit to receive mode, requires no software delays and eliminates timing problems and data collisions.

  • Jumpers JSPD and JEDG can further shorten the turn-around time to accommodate fast responding target devices.

  • Jumpers permit the RS485 termination and bias resistors to be user configured. J4 enables a loopback test mode.

  • The robust RS485 driver, with series protection resistors, and a full wave transcient suppression bridge, provide protection, and allows 32 standard loads at 4000 ft. at all data rates.

  • The 22 Ohm series protection resistors can be shorted out for long runs, or where the wire used has more resistance than usual.

  • Edge mounted LEDs display power and data activity at the RS485 and fiber interfaces.

  • Broad environmental range. 0C to +70C(32F to +158F). 10 to 90% RH(non-condensing)

  • Four(4) easy mount through hole standoffs, which accept #6 hardware, are provided on the circuit board.

  • User connections are the two fiber ports, a 3 position removable screw terminal strip for the RS485 port, and a terminal strip and barrel connector for the input power.

  • Accessories available are an enclosure, a wall wart power supply, fiber cables, and conformal coating. Contact us for options help.

  • R E Smith Inc makes a wide variety of isolated converters that address the electrical noise problems that contribute to unreliable communications, and product failure. If what you see here is not exactly what you need, don't hesitate in calling us at 513-874-4796.

  • We also have a new series of Converters and Repeaters that extend the RS485 communications distance far beyond conventional limits. Contact us for information on these leading edge problem solvers.

  • WARNING: Do NOT connect this device to a telephone system under any circumstances. Damage could result to the circuit board and/or your telephone system.

About R E Smith, Inc:

R E Smith, Inc. engineers and manufactures a comprehensive line of isolated and non-isolated converters, repeaters, multiport repeater hubs, fiber optic based products, and I/O boards. All our products are designed, built, tested, and shipped from our facility in the Greater Cincinnati Ohio area. We ship small quantities of most products from stock the same day, and larger quantities in a few business days.

We listen to you. We are customer driven. Many of our products were developed and improved due to suggestions and feedback from our word-wide customer base. They are being used at the South Pole, at the bottom of the sea, at the edge of space, and everywhere in between. Typical uses are very large networks, monitor and control of elevators, machinery, lighting, security, fire and alarm, access, cameras, military ground support, and much more. We provide free technical support, no-argument warranty repairs, and recommendations for your application. Challenge us with your communications problem. We may already have the solution. If your system keeps failing, or is unreliable, we have isolated, doubly isolated, noise resistant, cost effective, and proven solutions for difficult environments.

Related Files:

pdf icon F485CTrevC.pdf Converter schematic

Physical Properties and Features:

Fiber: Two ST Connectors
RS485: 3-position removable screw terminal strip.
Power: Barrel and 2 pin screw terminal strip.
LEDs RS485: Power(Yellow), data activity(TX: red, RX: green)
Fiber: Power(Yellow), data activity(TX: red, RX: green)
Bias: 620 Ohm pull-up and pull-down (jumper selectable)
Termination: 120 Ohm (jumper selectable)
Protection: Robust Driver with built in ESD tolerance, self resetting data fuses, and series resistors


Distance: Fiber: 1Km Min, RS485: Up to 4000 ft.
Operation: Fiber to 2 wire half-duplex RS485
Format: Asynchronous data with any combination of bits, parity, and stop (auto mode)
Speed: Up to 1Mbps
Environmental: 0C to +70C ambient, 10-90% RH(non-condensing)
Supply Voltage: 9-35 VDC
Power: Under 1/2 Watt(typical) + external load
Size: 2.50" X 2.00" X 0.9" (PC Board), with connectors: 2.50" X 2.15"
Mounting: 4 Holes at 2.00" X 1.50" (built-in standoffs for #6 hardware)

Options and Ordering Information:

F485CT: $195.00 ea. (Circuit board only)
Enclosure: $10.00 ea. (medium)
Power Adapter: $8.50 ea (wall wart type which meets most
California, and most world wide safety and efficiency standards)

This is the complete order number for the f485CT with all available options:

F485CT with all options (Power Supply and enclosure): Order Number: F485CT-BSPS @ $213.50 ea. (Qty. 1-9)

Need a different configuration or more information? Give Ron a Call at 513-874-4796 or 513-638-0228(Cell)

Webstore: F485CT

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