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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.
DARC44: Dual Channel RS485 to RS485 Repeater or Single Channel Converter


DARC44-C with Box

DARC44-C Label

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


Product Features:

  • This versatile auto transmit unit features fast bi-directional RS485/RS422 serial communications for office/indoor 2 wire and 4 wire point to point and multidrop networks

  • There are two independant RS485 channels that can also be configured as one RS422 channel, or one RS422 <-> RS485 converter.

  • Transparent to all asynchronous data, with any combination of data, parity, and stop bits, at data rates up to 230.4Kbps, without the need to set jumpers or switches. 

  • The RS485 transceiver provides fast auto turn-around to receive mode. It requires no software delays and eliminates timing problems and data collisions. We pioneered and perfected this leading edge technology long before our competition.

  • The RS485 transceivers operate in differential mode with built-in ESD tolerance, 22 Ohm series resistors, a transient suppression bridge, and auto-reset communications fuses. This provides robust protection from the interference commonly found in communication networks.

  • The driver allows 32 standard loads at 4000 ft. at data rates up to 230.4Kbps. When cascaded, these units can support very large isolated networks of RS485 devices. 

  • Jumpers allow the RS485 termination resistors to be user configured. Additional jumpers program the unit to one of its several configurations.

  • Edge mounted LEDs display power and data activity for each of the four transceiver ports.

  • A polarity protected high efficiency switching regulator accepts supply voltages from 9 to 35 VDC. Typical power consumption is under 1.0 Watts. 

  • 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 removable screw terminal strips for the RS485 ports, a removable screw terminal strip and a 2.1 mm barrel connector for the supply power. 

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

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

  • R E Smith has been producing and improving this mature product for many years. It is similar in function to the dual isolated DIFAR44 and DIACR44 units.

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

  • R E Smith Inc makes a wide variety of isolated devices 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 DARC44-CHA-RevA.pdf Repeater/Converter Channel A schematic Rev A
PDF Icon
Repeater/Converter Channel B schematic Rev A
PDF Icon
Physical Drawing Rev A



RS485 Connections: 5-wire removable screw terminal strips (RX/TX+, RX/TX-, Common)
Power: 2-wire removable screw terminal strip and 2.1mm barrel connector, 9-35VDC. Typical power is under 1.0 Watt
RS485 Bias: 620 Ohm pull-up and pull-down(fixed).
RS485 Termination: 150 Ohm (jumper selectable)
RS485 Protection: 8.2V Transient suppressors, 22 Ohm series resistors, and auto-reset communications fuses.
Indicators: Edge Mounted LEDs for data and power on all 4 ports.


Distance: Up to 4000 ft. (1220 meters) on each side of the interface
Operation: Dual 2 wire half-duplex RS485 repeater, or 4 wire repeater, or 2 wire to 4 wire converter
Format: Asynchronous data with any combination of data, parity, and stop bits
Speed: Up to 230.4Kbps
Environmental: -40 to +85C (-40 to +185F) ambient, 10 to 90% RH(non-condensing)
Power Req.: 9-35VDC, Under 1.0 Watt (typical) + external loads
Size: 4.50" X 3.50" X 0.9" (PC Board), with connectors:5" X 4"
Mounting: 5-Places 4.00" X 3.00" (built-in standoffs for #6 hardware)

Options and Ordering Information:

DARC44: $99.00 ea. (Circuit board only)
Enclosure: $10.00 ea. (Large)
Cable: None - screw terminal connections only
Supply: $8.50 ea. (12VDC/0.6A switching regulated wall power supply). Meets California, and most world wide safety and efficiency standards.

These is the DARC44 units showing the complete order numbers

For the DARC44-R(Repeater Configuration) with all options(enclosure and PS): DARC44-R-BPS @ $117.50 ea. (Qty. 1-9)
For the DARC44-C(Converter Configuration) with all options(enclosure and PS): DARC44-C-BPS @ $117.50 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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