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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.
DIFAR44: Dual Isolated RS485 to RS485 Repeater/Extender


DIFAR44 in Box

DIFAR44 Label

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


Product Features

  • This 3KV Isolated auto transmit unit features Bi-directional serial conversion from RS232 to RS422(4 wire full duplex point to point) or RS232 to RS485(2 wire half-duplex multidrop)

  • Optimized for Isolated office/indoor/outdoor point to point, or multi-drop systems.

  • The 3KV opto/galvanic isolation helps protect the unit from destructive transients often found in industrial and outdoor environments. 

  • Transparent to all asynchronous data, with any combination of data, parity, and stop bits, at data rates up to 115.2Kbps. 

  • In RS485 configuration it features fast auto turn-around, from transmit to receive mode, requires no software delays and eliminates timing problems and data collisions. We pioneered this leading edge technology long before our competition.

  • The RS422/RS485 transceiver is protected by auto-reset fuses, has built-in transient suppression and ESD tolerance. It can drive 32 standard loads at 4000 ft. at data rates up to 115.2 Kbps.

  • Jumpers allow the RS422/RS485 termination and bias resistors, and the RS422/RS485 mode to be user configured. The jumpers can also implement a loop-back configuration for testing purposes.

  • The RS232 side of the unit can be configured to accept  TTL/CMOS level signals.

  • Edge mounted LEDs display power, RX, and TX data activity at both interfaces. 

  • A polarity protected efficient 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 a 5 pin screw terminal strip for the RS232/TTL and supply power, and a 6 pin screw terminal strip for the RS422/RS485. 

  • 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 Inc makes a wide variety of isolated converters that address the electrical noise problems that contribute to unreliable communications, and product failure. 

  • 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 DIFAR44ArevE.pdf Repeater schematic Rev E
pdf icon DIFAR44BrevE.pdf Repeater schematic Rev E
pdf icon DIFAR44S.pdf Repeater schematic
pdf icon DIFAR44SSrevE.pdf Repeater schematic Rev E

Physical Properties and Features:

RS485: 3-wire removable screw terminal interface (RX/TX+, RX/TX-, Common)
Power: Removable 2-wire screw terminal interface with full wave bridge input, for 9-35VDC or 12-24VAC, typical power is under 1.0 Watt
RS485 Bias: 1.2K or 620 Ohm pull-up and pull-down (jumper selectable).
RS485 Termination: 120 Ohm (jumper selectable)
RS485 Protection: 8.2V Transient Suppressors in a diode bridge and auto-reset communications fuses on the data lines
Indicators: Edge Mounted LEDs for data and power on each port.


Distance: Up to 4000 ft. (1220 meters) on each side of the interface
Operation: 2-wire half-duplex RS485 repeater
Format: Asynchronous data with any combination of bits, parity, stop
Speed: Up to 230.4Kbps
Environmental:   -40 to 85C (-40 to 185F) ambient, 10-90% RH (non-condensing)
Power Requirements: 9-35VDC, (12-24VAC) Under 1.0 Watt (typical) + external load
Size: 4.50" X 3.50" X 0.9" (PC Board), with connectors: 5.00" X 4.00"
Mounting: 4-Places 4.00" X 3.00" (built-in standoffs for #6 hardware)

Options and Ordering Information:

DIFAR44: $169.00 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.

Complete order number for the DIFAR44 with all options: DIFAR44-BPS @ $187.50 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: DIFAR44

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