104-IIRO-16 Isolated Relay I/O Board


  • 16 optically-isolated, non-polarized CMOS compatible digital inputs accept ±31VDC or AC rms
  • IRQ on input change of state (COS) eliminates the need for constant polling
  • Slow/fast filter to accommodate AC voltages and noisy DC inputs
  • 16 long-life form C electro-mechanical relays switch up to 1A each

Factory Options: (call for pricing and availability)

  • Economy version without COS feature
  • Input only and relay only versions
  • Expanded input voltage levels
  • RoHS Available. Please contact us for ordering information
Last updated on December 7, 2023, 8:20 am


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Isolated Digital Input and Relay Output Card

The 104-IIRO-16 is a low-cost board that provides isolated input and output for PC/104 Bus computer applications. The board has sixteen optically-isolated digital inputs for AC or DC control signals and sixteen electro-mechanical relay outputs. The Change of State Detection capability of ACCES’ Model 104-IIRO-16 sets this board apart from the competition. An Economy version can be ordered as Model 104-IIRO-16E which has no Change of State Detection or IRQs. Also available is Model 104-RO-16 which has 16 relay outputs only.


The isolated inputs can be driven by either AC or DC and are not polarity sensitive. Input signals are rectified by opto-coupler diodes. A 1.8KΩ, ½ Watt resistor in series provides current limiting. The input voltage range is 3V to 28V (rms). To extend the input voltage range, you may connect external resistors in series with the input.

Each input circuit is switch selectable for slow/fast filter that has a 4.7 millisecond time constant. The filter must be selected for AC inputs in order to eliminate response to AC noise. The filter is also valuable for use with slow DC input signals in a noisy environment. The filter may be switched out for DC inputs in order to obtain faster response. Filters are manually switched individually on or off.


Interrupts are enabled/disabled by software. When the change-of-state detection circuit is enabled, the card asserts an interrupt whenever any of the sixteen isolated inputs change state. Once an interrupt has been generated and serviced, it is automatically cleared. This feature greatly frees up system resources by eliminating the need for constant polling to see when an input has changed state.


The electro-mechanical relay outputs are comprised of two groups of eight form C SPDT outputs.


The relay outputs are accessed via a 50 pin header type connector, while the isolated inputs are accessed via a 34 pin type header connector.


104-IIRO-16 utility software provided on CD includes sample programs in a variety of languages for DOS / Windows XP -> 10, both 32 & 64 bit. A Windows graphical setup program is also provided, and a “C” language sample for Linux.


Data Sheets



Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.

Isolated Digital Inputs

  • Number of Inputs: Sixteen
  • Type: Non-polarized, optically-isolated from each other and from the computer. (CMOS compatible).
  • Voltage Range: 3 to 31V DC or AC RMS (50 to 10 KHz)
  • Isolation: 500V
  • Input Resistance: 1.8KΩ in series with opto-coupler.
  • Response Time: 4.7 milliseconds w/filter, 10usec w/o filter

Electromechanical Relay Outputs

  • Number of outputs: Four SPDT form C
  • Contact Type: Single crossbar; Ag with Au clad
  • Carry Current: 2A
  • Rated Load AC: 0.5 A at 125 VAC (62.5 VA max )
  • Rated Load DC: 1 A at 24 VDC ( 30 W max )
  • Switch Voltage / Current: 125 VAC; 60 VDC / @ 1A (max)
  • Contact Resistance: 100 mΩ max
  • Max. Switching Voltage: 125 VA, 60 VDC
  • Max. Switching Current: 1A
  • Max. Carrying Current: 2A
  • Contact Life-mechanical: 5,000,000 operations min
  • Operating / Release Time: 5 ms max (mean value: approx 2.5 ms, and 0.9 ms respectively)


  • When enabled by software, interrupts are generated when any digital input changes state (High to Low or Low to High, and from signal to no signal with AC inputs).

Power Required

  • +5VDC at 0.5A (all relays ON).


  • Ambient Temperature: Operating: -30°C to 70°C. (non-icing)
  • Weight: Approx. 4.5 oz. (~130 grams).

CE testing & approval must be done at the system level, in the designed enclosure, and is not done on individual boards.

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