USB Isolated Input and Relay Output Digital I/O Modules


  • High-speed USB 2.0 device, USB 3.0 compatible
  • 16 optically isolated inputs
  • 16 Form C electromechanical 1A relays
  • PC/104 module size (3.550" by 3.775") and mounting compatibility
  • Stackable or unstackable USB/104 OEM embedded board
  • Alternate micro-fit embedded USB header connector
  • Custom high-speed function driver (non-HID)
  • Type B USB connector features industrial strength and high-retention design
  • LabVIEW VI driver


  • Eight or four input/output versions available
  • Input only and relay only versions
  • External power and AC/DC adapter
  • Extended operating temperature (-40°C to +85°C)
  • DIN rail mounting provision
  • RoHS Available. Please contact us for ordering information

Model USB-IIRO-16-OEM is an ideal portable solution for adding easy-to-install isolated input and relay output digital I/O capabilities to any PC or embedded system with a USB port. Featuring 16 Form C (SPDT) electromechanical relays and 16 optically isolated digital inputs, the unit is the smallest of its kind for digital monitoring and control using USB.

The isolated, non-polarized inputs may be driven by either DC sources of 3-31 V (or higher by special order) or AC sources at frequencies of 40 Hz 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. The input channels are available via a 34-pin IDC type vertical header. The relay outputs are de-energized at power-up to prevent an unintended control output signal. Data to the relays is latched. The relay contacts are available via a 50-pin IDC type vertical header.

The USB-IIRO-16-OEM, like the PC/104 and PCI versions, is excellent in applications where on-board relays are required and inputs must be isolated such as in test equipment, instrumentation, and process control. The USB-IIRO-16-OEM is a USB 2.0 device, offering the highest speed available with the USB bus. It is fully compatible with both USB 1.1 and USB 2.0 ports. The board is plug-and-play allowing quick connect or disconnect whenever you need additional I/O on your USB port.

The USB-IIRO-16-OEM is designed to be used in rugged industrial environments, with extended temperature available. The board is PC/104 sized (3.550 x 3.775 inches, 90mm x 96mm) for added flexibility in embedded applications and is small enough to fit nicely onto any desk or testing station.


The OEM (board only) version is perfect for a variety of embedded applications. What makes the OEM option unique is that its PCB size and pre-drilled mounting holes match the PC/104 form factor (without the bus connections). This ensures easy installation using standard standoffs inside most enclosures or systems. The board can be added to any PC/104, PCI-104, or PCI/104-Express stack by connecting it to a USB 2.0 port usually included on-board with embedded CPU form factors such as EBX, EPIC, and PC/104. This is especially important since many newer CPU chipsets do not support ISA and have plenty of USB ports. Future stacks will be using the extremely fast PCI Express bus which is essentially overkill for simple monitoring and control. For embedded OEM type applications, an additional micro-fit USB input header is provided.

High Retention USB Connector

The ever-growing presence of USB in the industrial/military marketplace has driven the need for USB connections to be reliable, dependable, and unfailing. Gone are the days of loose USB connections. A type B USB connector is used on all ACCES USB/104 products which features a high retention design that complies with the class 1, Div II minimum withdrawal requirement of over 3 pounds of force (15 Newtons). This connector has an orange color-coded insulator to quickly differentiate it from standard USB connectors. Using these USB connectors increases reliability in your system and ensures a tight connection. For embedded OEM type applications, an additional micro-fit USB input header is provided.

Optional Enclosure

The USB-IIRO-16-OEM is available packaged in a rugged, steel enclosure with an attractive black powder coat finish and an anti-skid bottom. The enclosure is useful in industrial environments and protects the board from potential environmental hazards. The unit enclosure is 4 inches wide by 4 inches deep by 1.4 inches high and features a DIN rail mounting provision. Please visit the USB-IIRO Series webpage to order the enclosed unit.

USB-IIRO-16 BoardUSB-STB-84 InstalledTerminals WiredReady to Go!


The industrial I/O market commonly uses electromechanical Form C relays due to their robustness and ability to withstand unexpected surge currents allowing for increased flexibility in switching capability. These relays are also used where small reed relays are inadequate due to their susceptibility to contact damage. The USB-IIRO-16-OEM can be used in the following markets.

  • Mobile Solutions
  • Test Equipment
  • Kiosks
  • Robotics
  • Machine Control
  • Monitoring and Control
  • Security Systems, Energy Management
  • Industrial Automation
  • Embedded OEM

Optional Accessories

Available accessories include a wide variety of cables and screw terminal boards for quick and easy connectivity. Also, a DIN rail mounting provision and a 5V regulated external AC/DC power supply are offered.

Drivers and Downloads

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..

USB and Performance

Our USB Data Acquisition products use our "AIOUSB" driver package in Windows and Linux. This driver package includes 32-bit and 64-bit support, and consists of low-level driver components and a high-level API library. This custom interface driver enables our USB devices to achieve 4000 transactions per second, compared to the competitions' "HID" drivers that cap out around 50 transactions per second. You can read all about the API in the USB Software Reference Manual linked below, and included in every applicable Software Package. (The Linux version of the AIOUSB API is almost identical to the Windows API, and is documented in the aiousb.html file included in the Linux software package.) Like all of our software, full source code is always provided.

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.

Available Reference Manuals

Available Software Downloads

Available Datasheets

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 Inputs

  • Number: Sixteen
  • Type: Non-polarized, optically isolated from each other and from the computer (CMOS compatible)
  • Voltage: 3 to 31 DC or AC RMS (40Hz to 10kHz)
  • Isolation: 500V* (see manual) channel-to-ground and channel-to-channel
  • Resistance: 1.8K ohms in series with opto-coupler
  • Filter Response: Rise Time = 4.7 mS / Fall Time = 4.7 mS
  • Non-Filter Response: Rise Time = 10 uS / Fall Time = 30 uS

Relay Outputs

  • Number: Sixteen SPDT form C
  • Contact Type: Single crossbar; Ag with Au clad
  • AC Load: 0.5 A at 125 VAC (62.5 VA max.)
  • DC Load: 1A at 24 VDC (30 W max.)
  • Switching Voltage: 125 VAC, 60 VDC max.
  • Switching Current: 1A max.
  • Contact Resistance: 100 mOHM max
  • Contact Life: mech’l: 5 million operations min.
  • Operating Time: 5 msec max.
  • Release Time: 5 msec max.


  • Operating Temperature Range: 0° to 70°C (optional -40°C to +85°C)
  • Storage Temperature Range: -40° to +85°C
  • Humidity: Maximum 90% RH, without condensation
  • Board Dimension: 3.550 x 3.775 inches


  • 5VDC @ ~ 30mA typical (all relays off, add 30mA per relay)
  • 5VDC @ ~ 510mA typical (all relays ON)
  • +5VDC derived from the USB bus cable or external power supply depending on the user configuration.

The USB bus is specified to provide 500mA through the USB cable to most desktop environments. For example, is you are using eight relays, you would only require +5VDC 270mA (30mA x 8) for full relay use. This would be lower than the maximum cable current capacity of USB. If you are using more than 500mA, or your USB port/hub has less then the 500mA normally provided, use optional 5VDC external power supply (-PR option) and remove VUSB jumper and place jumper on VEXT. Then plug in external power before plugging into USB port.

Regulatory Compliance

  • This product is designed to be in full compliance with CE requirements.
ModelPrice (USD)

USB-IIRO-16-OEM16 isolated inputs and 16 relay outputs
USB-II-16-OEM16 isolated digital inputs only version
USB-RO-16-OEM16 relay outputs only version
USB-IIRO-8-OEM8 isolated digital inputs and 8 relay outputs version
USB-IIRO-4-OEM4 isolated digital inputs and 4 relay outputs version
USB-STB-84Internal plug-in screw termination board $79
STB-50DIN rail mountable screw terminal board for 50-pin header type connector $44
C104-50F-1250-pin ribbon cable with female headers, 12" long $15
STB-34DIN rail mountable screw terminal board for 34-pin header type connector $44
C104-34F-1234-pin ribbon cable with female headers, 12" long $12
C104-50F-D25M50-pin ribbon cable with female header to 2 DB25M connectors, 12" long $19
C34FF12DF3734-pin ribbon cable with female header TO DB37 female connector, 12" long $19
MP104-DINDIN rail mounting provision $19
CUSB-EMB-11ft USB Type A to micro-fit OEM header $19
CUSB-EMB-66ft USB Type A to micro-fit OEM header $19
CUSB-EMB-HDR30" USB 1x5 standard header to micro-fit OEM header $19
CUSB-EMB-HDRM30" USB 1x5 metric header to micro-fit OEM header $19
CUSB-EMB6" micro-fit to micro-fit embedded OEM cable $19
Model Options (call for pricing)
-PR+5VDC external power jack and regulated AC/DC adapter
-TExtended operating temperature (-40°C to +85°C)

Acquisition, Control, Communication: Engineering and Systems

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