Rugged Ethernet IO Device with 4 Digital Inputs & 4 Relay Outputs

DIN Icon

Temperature Icon

4 Inputs

4 Relays Icon

Web Interface Icon

Ethernet Icon

Modbus TCP Icon



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  • Rugged Design - Operating temperature, -40°C ~ 70°C
  • Intuitive embedded web interface for configuration
  • 4 Inputs and 4 Relay Outputs for monitor and control applications
  • Supports SNMP 1, 2c, 3, & SNMP Traps 1, 2c
  • Supports DNP 3.0 over Ethernet
  • Supports Modbus over Ethernet
  • Use the System Link feature to Pair units together for bi-directional alarm transportation over Ethernet
  • Email alarming for Inputs and Outputs, emails are customizable
  • Advanced SMTP integration allowing for SSL and TLS based authentication
  • Event log with time stamps
  • Each digital input is optically isolated
  • System power ranges available: 24-48VDC or 125VDC
  • 10/100 Fast Ethernet Port
  • Limited Lifetime Warranty

  • Made in USA

Smart Series

Ethernet IO

This Smart IO device is an Ethernet device with 4 Integrated controllable relays and 4 integrated digital inputs. The device allows for web based control and monitoring of it's relays and inputs and may be integrated into distributed control and network management systems. Each of the Relays and inputs can be individually configured to send customized emails and notifications. The device supports a wide variety of protocols that it is compatible with over Ethernet. Supported integration protocols: SNMPv1,2c,3, SNMP Traps (SNMP 1, 2vc), Modbus TCP featuring addressable registers, and DNPv3 TCP for integration with utility and other automation control systems.

Bi-Directional Contact Closure over Ethernet

When using RLH's System Link feature, two of these devices can link up and establish a tunnel over an Ethernet network. When a link is established between two Smart IO devices the outputs at each location will mirror the input states at the opposite end. Providing bi-directional alarming between two locations over an Ethernet network.


For a comprehensive review of the product specs, please see the Data Sheet, or feel free to contact us with any questions.

Powering Voltage:
Standard Model - 24-48VDC
-A Model - 125VDC
-B Model - 12VDC

Power Consumption:
6 Watts (Maximum)

Protocols Supported:
DNP 3.0 TCP, Modbus TCP, SNMP Polling 1,2c,3, SNMP Traps 1, 2c, SMTP w/ TLS Authentication

System Link Response Time:
Typical 8ms, Maximum 45ms

*Specifications listed are based on direct connections. Network overhead should be considered when calculating overall system response times.

Data Interface:
Ethernet (RJ-45)

Data Rate:
Fast Ethernet 10/100Mbps

Inputs 1~4:
Polarity Insensitive
Optical isolation 3.5kV
SM-IO-XX-DR-2 Dry: Sourcing Input (100 ohms maximum loop resistance)
SM-IO-XX-24-2 Wet: Sinking Input (8~27VDC / 5mA)
SM-IO-XX-48-2 Wet: Sinking Input (20~52VDC / 5mA)

Relay Outputs 1~4:
115VAC / 1.08A / 125VA
12VDC / 3.00A / 36 Watts
24VDC / 2.50A / 60 Watts
48VDC / 1.25A / 60 Watts
130VDC / 0.46A / 60 Watts
220VDC / 0.27A / 60 Watts

LNK - System Link ON/OFF Status
Inputs - ON/OFF Status
Outputs - ON/OFF Status

System Alarm Output:
NO/NC Relay

Surge Protection:
Varistors & Automatic resettable fuses
DC Input Isolation 1.5kV
Voltage Reversal Protection

Powder coated steel and aluminum alloy
Physical Dimensions H 5.0” x W 2.0” x D 3.9” (127mm x 51mm x 100mm)

Mounting Style:
Standard DIN rail (T-35)

Temperature -40°F to +158°F (-40°C to +70°C)
Humidity 95%
MTBF 175,000 Hrs. (Circuit Board level)

Limited Lifetime

When used as a pair: Contact Closure over Ethernet

When used as a pair: Contact Closure over Ethernet

When used as a standalone device: Remote I/O

When used as a standalone device: Remote I/O


Download the RLH Data Sheet

Download the RLH User Guide

Download the RLH MIB Table

Download the RLH DXF File

Download the RLH Step File

  • Add -A to the end of the part number for 125VDC input powering option
  • Add -B to the end of the part number for 12VDC input powering option

Please submit a quote request or contact your RLH sales representative for pricing and delivery information.