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36-Channel PC/104

Isolated Input/Relay Module



  • 32 Optically Isolated Non-Polarized digital inputs
  • Change of State (COS) Detection
  • Interrupt Sharing
  • 3 to 31 Volt AC or DC Signals
  • Switchable Slow/Fast Filters
  • Schmitt Trigger buffers
  • Designed, made, supported, and manufactured in the USA


  • 4 Form C (NC, NO, C) SPDT Relays
  • Contact ratings 24VDC @ 1A and 115VAC @ 0.5A
  • +5V power with onboard 0.5A resettable fuse for external circuits

  • RoHS Available. Please contact us for ordering information
  • Model 104-II32-4RO is a 36-channel PC/104 utility board featuring 32 fully optically isolated digital inputs and four handy relay outputs. The inputs may be driven by either DC sources of 3-31V (or higher by special order) or AC sources at frequencies of 40Hz to 10KHz. Optically isolating the digital inputs from each other, and from the computer, assures smooth, error-free data transmission in noisy, real-world environments. All I/O connections are made via one 34-pin and one 50-pin right angle header (vertical headers available upon request).

    Each input circuit includes a jumper selectable slow/fast filter to accommodate AC inputs and is also useful for slow DC inputs in noisy environments. The filter may be manually disabled to increase the boards typical response time to 10 usec when used with faster DC inputs. The input impedance is 1.8K Ohms to accommodate a wide input range. To prevent erroneous input state change detections and interrupts, Schmitt triggers are used which provides a solid logic signal to the computer interface.

    The electromechanical relays are more flexible than FET and solid state outputs in regards to the kind of signals that can be switched. Another cool feature of the board is a fused +5V at the connector which can be used with a wrap plug for an easy test setup to quickly verify proper operation of the boards 32 inputs, change of state detection IRQs and 4 relays without any additional test equipment!

    System interrupts are software controlled, enabling the board to generate an interrupt whenever one or more of the isolated digital inputs changes state. When an interrupt is received a provided ISR (Interrupt Service Routine) handles the request, polls the card once to read the state change then clears the interrupt, enabling the board to detect the next change without processor intervention. IRQ Sharing with other ISA system devices is enabled for ease of system development and installation.

    This 8-bit (16-bit pass through connectors) PC/104 board can be installed in any embedded system that supports PC/104 or PC/104+ modules. I/O connectors ship standard as right angle pin type but can also be ordered as vertical to avoid obstructions by other system components or enclosure constraints. This high-density I/O board is available with a variety of options such as an economy version (no-COS), extended (-40 to +85 C) temperature, higher input ranges, without relays, etc. Let us know what you need for your OEM application and well supply it, saving you time and money by buying only what you need.

    If youd like this board delivered in an embedded system, wed be glad to provide integration at a competitive rate. Consider using it as part of our award-winning IE-DAS Embedded System or our rugged E4-DAS Fanless Embedded Computer. For complete details on that and our other fine products then give us a call at 800-326-1649 and speak with an application specialist that can help find a solution that is right for you and your project.

    The 104-II32-4RO is supported for use in most operating systems and includes a free DOS, Linux and Windows 95/XP -> 10, both 32 & 64 bit compatible software package. This contains sample programs and source code in Visual Basic, Delphi, and Visual C++ for Windows. Also incorporated is a graphical setup program in Windows. Third party support includes a Windows standard dll interface usable from the most popular application programs. Linux support consists of installation files and basic samples for programming from user level via an open source kernel driver.

    Available Reference Manuals

    Available Software Downloads

    Available Datasheets

    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 Windows XP through Windows 10, including "Server 2008," "Embedded," and "Compact" flavors in both 32-bit and 64-bit 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 Visual C# and Delphi with many devices including samples in Visual Basic and Visual C/C++, as well as Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and demonstration VIs for many of 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 Linux kernels 2.6 and newer and recent 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 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.

    non-plug-and-play driver install guide for Windows

    Please refer to the Non-PnP Install Guide for instructions to get your PC/104 and ISA bus devices installed in modern Windows.

    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 and Type: 32, non-polarized, optically isolated from each other and ground
    • Voltage Range: 3 to 31 volts DC or AC Rms ( 40 to 10000 Hz ), CMOS compatible
    • Isolation: 500V*(see manual) channel-to-ground and channel-to channel
    • Input Resistance: 1.8K ohms in series with opto coupler (two LEDs)
    • Response Time: 4.7 mSec w/filter, 10 µSec w/o filter (typical)

    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)


    • Generated when inputs change state if enabled by software and jumper selected IRQ
    • IRQ Sharing via tri-stated line driver on jumper selected interrupt line (positive edge true)

    Power Required

    • +5 VDC @ 150 mA (all inputs HI & all relays ON, no load on fused 5V power)
    • +5 VDC power is provided via a resettable polyfuse (at 0.5A) for application and general purpose usage


    • Operating Temp: 0° to +70°C
    • Storage Temp: -40° to +80°C
    • Weight: 3.02 oz

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

    ModelPrice (USD)

    Acquisition, Control, Communication: Engineering and Systems