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Give Ron a Call at 513-874-4796 or 513-638-0228 for additional information.
RSFC2: RS232 to RS485 Asyncronous Converter with Precision Microprocessor Timing




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

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

  • 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.

  • 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, and DSR. The RSFC2 does not require these, or 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. and 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.

  • 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 an RJ11/12 telephone style jack for the RS232, a 4 pin Wago style terminal strip and 2 RJ11/12 jacks for the RS485 port, and a 2.1 mm barrel connector and a 4 pin Wago style terminal strip for power.

  • Accessories available are a 12VDC Switching Power Supply(Wall Wart), an enclosure, and a 7ft DB9F to RJ11/12 RS232 cable.

  • Conformal Coating, cable, and connectors, are factory options. Contact us for options help.

  • R E Smith Inc also provides a functionally identical unit with different connectors, LEDs, and a DIN rail mount: RSFC2DIN.

  • 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 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/physical Rev. B1

Physical Properties and Features:

RS232: RJ11/12 Jack, 3 wire(TX, RX, Common)
RS485: Wago Style terminal strip, and 2 RJ11/12 Jacks(RS485+, RS485-, Common)
Power: 2.1mm center positive "Barrel" connector, and 4 pin Wago style terminal strip
LEDs RS485 Data activity
Bias: 910/2.2K Ohm pull-up and pull-down (jumper selectable)
Termination: 120 Ohm (jumper selectable)
Protection: Transient Voltage Suppressors inside a diode bridge, auto-reset communications fuses, ESD tolerance.


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

Options and Ordering Information:

RSFC2: $95.00 ea. (Circuit board only)
Enclosure: $10.00 ea. (Medium)
Cable: $7.50 ea. (RS232, 7 ft., specify DB9F-7 or DB25F-7)
Supply: $8.50 ea. (9VDC @ 200/300 mA wall power supply)
Meets California, and most world wide safety and efficiency standards 

This is the RSFC2 configuration showing the complete order number

RSFC2 with all options (DB9F cable/Enclosure/PS): Order Number: RSFC2-B9FSPS @ $121.00 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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