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Give Ron a Call at 513-874-4796 or 513-638-0228 for additional information.
IRSFC24FB 3 KV Opto/Xformer Isolated RS232 to RS485 2 Wire Half Duplex Converter/Repeater




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


Product Features:

  • This 3KV Isolated auto transmit unit will be factory configured as a bi-directional serial converter, or repeater, in 2 wire half-duplex communications mode.  

  • Optimized for Isolated office/indoor/outdoor 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 115.2Kbps. 

  • Fast auto turn-around, from transmit to receive mode, requires no software delays and eliminates timing problems and data collisions. We pioneered and perfected this leading edge technology long before our competition.

  • The isolated RS485 transceiver is protected by auto-reset fuses, a transient suppressor bridge, and built-in ESD tolerance. It can drive 32 standard loads at 4000 ft. at data rates up to 115.2 Kbps.

  • When configured as a repeater, the unisolated RS485 transceiver is protected by its built-in ESD tolerance. This side of the unit is intended to be connected to the system by a short cable run.

  • A jumper allows removal of the RS485 termination, and several jumpers enable multiple levels of bias in order to optimize performance in less than ideal system configurations.

  • Edge mounted LEDs display regulated power, and RX and TX data activity. 

  • A polarity protected switching power regulator accepts supply voltages from 9 to 35VDC, at 0.5 Watts max. 

  • Broad environmental range. Temperature: -40C to +85C(-40F to +185F). Humidity: 10 to 90% RH(non-condensing)

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

  • User connectors are 3 pin removable terminal strips for the isolated RS485, and the unisolated RS485/RS232, and a 2 pin screw terminal strip for the power. 

  • Accessories available are a 12VDC Switching Power Supply(Wall Wart), and an enclosure. No cables are available for this unit 

  • Conformal coating, and connectors, are factory options. 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.

  • R E Smith Inc has similar converters with comparable/enhanced performance. They feature different connectors, LEDs, and termination options. Check out the IRSFC24, IRSFC24H, and IRS422HV. 

  • We also have a new series of Converters and Repeaters that extend the RS485 communications distance far beyond conventional limits.

  • If what you see here is not exactly what you need, don't hesitate in calling us at 513-874-4796.

  • 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 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
Converter schematic rev C


RS232/RS485: Converter: 3-wire removable terminal strip(TX, RX, Common)
Repeater: 3-wire removable terminal strip(RXTX+, RXTX-, Common)
RS485 (Isolated side): 3-wire removable terminal strip(RXTX+, RXTX-, Common)
Power: 2 wire screw terminal strip
LEDs Edge mounted regulated power, and RS485 Data activity
Bias: 1K/4.7K/10K Ohm pull-up and pull-down (8 jumper selectable combinations)
Termination: 220 Ohm (jumper selectable)
Protection: Transient Suppressors inside a diode bridge, auto-reset communications fuses, Sipex SP485REP/EEP Transceiver with built-in ESD tolerance, 3KV optical isolation.


Distance: Up to 4000 ft. (1220 meters)
Operation: 2-wire half-duplex RS485
Format: Asynchronous data with any combination of data, parity, and stop bits
Speed: Up to 115.2Kbps
Environmental: -40C to +85C ambient, 10-90% RH non-condensing
Supply Power: 9-35VDC at 0.5 Watts typical + external loads
Size: 3.50" X 3.00" X 0.9" (PC Board), with connectors: 3.50" X 3.25"
Mounting: 4-Holes at 3.00" X 2.25" (built-in standoffs for #6 hardware)

Options and Ordering Information:

IRSFC24FB-C/R: $109.00 (C)/$149.00 (R) ea. (Circuit board only)
Enclosure: $10.00 ea. (Medium)
Cable: No cable is available for this unit
Supply: $8.50 ea. (12VDC/0.5A switching regulated wall power supply). Meets California and most world wide safety and efficiency standards.

This the IRSFC24FB-C (Converter) unit showing the complete order number

IRSFC24FB-C with all options (Enclosure/PS): Order Number: IRSFC24FB-C-BSPS @ $127.50 ea. (Qty. 1-9)

This the IRSFC24FB-R (Repeater) unit showing the complete order number

IRSFC24FB-R with all options (Enclosure/PS): Order Number: IRSFC24FB-R-BSPS @ $167.50 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: IRSFC24FB-C (Converter) & IRSFC24FB-R (Repeater)

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