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RSFC2DIN : RS232 to RS485 Asyncronous Converter with Precision Microprocessor Timing




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


Product Features:

  • This microprocessor controlled auto transmit unit features Bi-directional serial conversion from RS232 to RS485 in 2 wire half-duplex communications mode.

  • This unit is functionally identical to the RE Smith Product RSFC24. Only the connectors and LED indicators are different.

  • User accessable jumpers can set the specific baud rate and character mode of communications. User can also select one of two automatic modes which accomodate a broad range of data rates. See the schematic referenced below.

  • Using this jumper defined information, the dedicated microprocessor returns the unit to the receive mode automatically, without any software intervention. The precision of this turn-around eliminates missed bits and data collisions, even from fast responding target devices.

  • Pull-up resistors are built-in to accomodate devices that need inputs: CTS, RTS, DTR, and DSR. This unit does not require these, nor any other control signals, to operate at maximum performance.

  • 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 115.2Kbps. 

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

  • Jumpers allow the RS485 termination, two levels if bias resistors, and the RS232 DTE/DCE mode to be user configured. Jumper J13 will place the unit in Loop-back mode for self test. 

  • Board mounted LEDs display Transmit(TX) and Receive(RX) data activity. Edge mounted LEDs display the regulated power and the TX and RX data activity at the RS485 interace.

  • A bridge protected switching power regulator accepts supply voltages, from 9 to 35 VDC, or 12-24VAC at 0.5 Watt typical. 

  • 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 connections are: DB9M for the RS232, and a 6 pin screw terminal strip for the RS485 port and the supply power.

  • Accessories available are a 12VDC Switching Power Supply(Wall Wart), and an enclosure with DIN clip.

  • Conformal Coating, cable, 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.  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 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
Converter schematic rev B


RS232: 3-wire interface to DB9M (TX, RX, Common)
RS485: 4 position screw terminal strip (RS485+, RS485-, Common [2 places])
Power: 2 position screw terminal strip
LEDs Board mounted RS485 Data activity and edge mounted power and data activity
Bias: 910/2.2K Ohm pull-up and pull-down (jumper selectable)
Termination: 120 Ohms (jumper selectable)
Protection: Transient Voltage Suppressors inside a diode bridge, auto-reset communications fuses, ESD tolerance


Distance: Up to 4000 ft. (1220 meters)
Operation: 2-wire half-duplex RS485
Format: Fixed or automatic asynchronous data with many combinations of data, parity, and stop bits
Speed: Up to 115.2Kbps (employs skew rate limited driver)
Environmental:   -40 to 85C ambient, 10-90% RH non-condensing
Supply Power 9-35VDC or 12-24VAC at 0.5 Watts (typical) + external load
Size: 3.50" X 2.75" X 0.9" (PC Board), with connectors: 3.50" X 3.0"
Mounting: 4-Holes at 3.00" X 2.25" (built-in standoffs for #6 hardware)

Options and Ordering Information:

RSFC2DIN: $119.00 ea. (Circuit board only)
Enclosure: $12.00 ea. (Medium with DIN Clip)
Cable: No cable available for this product (DB9M onboard)
Power Supply $8.50 ea. (12VDC/0.5A switching regulated wall power supply). Meets California and most world wide safety and efficiency standards

This is the RSFC2DIN configuration showing the complete order number

RSFC2DIN with all options (enclosure with DIN clip and power supply): Order Number RSFC2DIN-BPS @ $139.50 ea. (Qty. 1-9)

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


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