Solid State I/O Modules and 1781-A24A, 1781-A24H, 1781-A16A, 1781-A4T, and 1781-A8A Mounting Boards


  • Industry standard, opto-isolated digital I/O modules
  • Choice of AC or DC inputs or outputs
  • Screw terminals for easy interface to field wiring
  • Edge connectors for interface to digital I/O cards via ribbon cable
  • 4000V optical isolation
  • Slim design to save space
  • Alumina substrate provides superior heat dissipation

The solid-state relay I/O modules are used as power control and voltage monitoring interfaces between high level DC or AC lines and TTL logic levels. The modules are in a slim, space-saving form. Four functions are offered: DC Input, DC Output, AC Input, and AC Output.

The A24A can hold up to 24 modules. Field-side terminations are provided via convenient terminal strips with points isolated from each other. The logic side has a common logic supply bus with screw terminals for input power connections. Logic-side connections are via a 50-conductor edge connector.


Any of ACCES' buffered digital I/O cards (IOD-24, IOD-48S, IOD-72, or IOD-120) may be used and one 24-bit port will be used per A24A. Various combinations of I/O modules can be intermixed on one A24A mounting card. However, each contiguous group of eight channels must contain only input or output modules. If more than 24 I/O modules are required, additional 24-bit ports may be necessary.

In some cases, logic power required can exceed the current handling capability of digital I/O cards. For these instances, an external 5 VDC power supply is recommended. Screw terminals are provided on the card for those power supply connections in addition to a jumper next to the terminal strips that should be cut.

Available Datasheets

Drivers and Downloads

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

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.



  • Operating Temperature Range: -30° to +80°C.
  • Storage Temperature Range: -40° to +100°C.
  • Isolation: 4000 V.
  • Input-to-Output Capacitance: 8pF.
  • Mounting Card Dimensions: 14.05" long x 3.50" wide.
  • Module Dimensions: 1.70" long x 0.43" wide.

DC Input Modules

Input IB5S (IDC5B Type) IN5S¹ (IDC5 Type)
Input Voltage Range 3.3 - 32 VDC 10 - 60 VDC/AC rms
Input Resistance 1 KW N/A
Max. Input Current² 24 mA 24 mA
Drop Out Current 1.0 mA 1.0 mA
Max. Offstate Voltage 2.0 VDC 2.0 VDC / VAC rms

Output IB5S (IDC5B Type) IN5S¹ (IDC5 Type)
Logic Supply Voltage 5.0 VDC 5.0 VDC
Logic 0 Voltage Range (@ pin 3) 1.5 - 6.0 VDC 1.5 - 6.0 VDC
Typical Logic Supp. Current² 10 mA 10 mA
Max. Output Leakage Current³ 10 µA 10 µA
Max. Turn-On Time 300 µSec 20 mSec
Max. Turn-Off Time 600 µSec 30 mSec

DC Output Modules

Input OB5S (ODC5 Type) OC5S (ODC5A Type)
Nominal Input Voltage 5.0 VDC 5.0 VDC
Input Voltage Range 2.5 - 7.5 VDC 2.5 - 7.5 VDC
Drop Out Voltages 1.0 VDC 1.0 VDC
Max. Input Current 27 mA w/o LED 27 mA w/o LED
Typical Input Current 10 mA DC 10 mA DC
Nominal Input Resistance 240 W 240 W

Output OB5S (ODC5 Type) OC5S (ODC5A Type)
Max.Line Voltage 60 VDC 200 VDC
Min. Line Voltage 3.0 VDC 5.0 VDC
Max. Off State Voltage 60 VDC 200 VDC
Max. Off State Leakage 1.0 mA DC 2.0 mA DC
Max. On State Current 3.0A DC4 1.0A DC5
Min. On State Current 10 mA DC 10 mA DC
Max 1-Second Surge 5A DC 5A DC
Peak On State Voltage @ 25°C 1.5 VDC 1.6 VDC
Max. Turn-On Time 50 µSec 50 µSec
Max. Turn-Off Time 100 µSec 100 µSec

AC/DC Input Modules

Input IA5S¹ (IAC5 Type) IM5S¹ (IAC5A Type)
Nominal Input Voltage 120 Vrms / DC 249 Vrms / DC
Input Voltage Range 90 - 140 Vrms / DC 180 - 280 Vrms / DC
Maximum Input Current³ 10 mA rms 8 mA rms
Drop-Out Current 2.5 mA rms 1.5 mA rms
Max. Off-State Input 3.0 mA rms 2.0 mA rms
Max. Off-State Voltage 50 Vrms / DC 120V rms

Output IA5S¹ (IAC5 Type) IM5S¹ (IAC5A Type)
Logic Supply Voltage 5.0 VDC 5.0 VDC
Logic 0 Voltage Range (@ pin 3) 1.5 - 6.0 VDC 1.5 - 6.0 VDC
Typical Logic Supp. Current² 10 mA DC 10 mA DC
Max. Logic Supp. Current³ 18.5 mA 18.5 mA
Max. Logic Supp. Leakage³ 10 µA 10 µA
Max. Output Voltage 30 VDC 30 VDC
Max. Output Current 50 mA DC 50 mA DC
Max. Output Leakage Current³ 10 µA 10 µA
Max. Output Voltage Drop6 200 mV 200 mVDC

AC Output Modules

Input OA5S¹(OAC5 Type) OM5S (OAC5A Type)
Nominal Input Voltage 5.0 VDC 5.0 VDC
Input Voltage Range @ pin 3 2.5 - 7.5 VDC 2.5 - 7.5 VDC
Drop-Out Voltage 1.0 VDC 1.0 VDC
Max. Input Current 27 mA w/o LED 27 mA w/o LED
Typical Input Current7 10 mA 10 mA
Nominal Input Resistance 240 W 240 W

Output OA5S¹(OAC5 Type) OM5S (OAC5A Type)
Nominal Line Voltage 120 Vrms 240 Vrms
Line Voltage Range 12 - 140 Vrms 24 - 280 Vrms
Max. Peak Off-State Voltage 400 V 600 V
Max. Off-State Leakage 2.5 mA rms 4.5 mA rms
Static Off-State (dv/dt) 200 V/µSec 200 V/µSec
Max. On-State Current4 3.0A rms 3.0A rms
Min. On-State Current 50 mA rms 50 mA rms
Max. 1-Cycle Surge 100A peak 100A peak
Peak On-State Voltage 1.6V peak 1.6V peak


1. Can be used with either DC or AC inputs.
2. At nominal voltage with LED on board.
3. At maximum logic voltage.
4. Derate 33 mA/°C above 25°C.
5. Derate 20 mA/°C above 60°C.
6. At maximum output current.
7. LED in series w/nominal voltage.

Regulatory Compliance
Declaration of Conformity, and Test Reports are on file. Users must use appropriate shielded cables.

Please note, prices below require a minimum order quantity of 10 pieces, please call for all other quantities.

ModelPrice (USD)

Acquisition, Control, Communication: Engineering and Systems

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