Rugged Ethernet IO Device with 4 Digital Inputs for Monitoring and Alarming

DIN Icon

Temperature Icon

4 Inputs

Web Interface Icon

Ethernet Icon

DNPv3 TCP Icon

Modbus TCP Icon


PoE Icon

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  • Rugged Design - Operating temperature, -40°C ~ 70°C
  • Intuitive embedded web interface for configuration
  • 4 Inputs for multiple alarm monitoring
  • 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 with a Relay Output unit alarm transportation over Ethernet
  • Supports a One-to-Many Feature, Send alarms from one location to multiple Relay Output devices
  • Email alarms for the Inputs are customizable to your application
  • 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
  • PoE Powered device - Can be powered by any IEEE 802.3af compliant PoE source
  • 10/100 Fast Ethernet Port
  • Limited Lifetime Warranty

  • Made in USA

Smart Series

Ethernet I/O

The Smart Input Sensor is a Ethernet device with 4 digital inputs. The device allows for web based monitoring of the inputs and may be integrated into distributed control and network management systems to allow those systems to alarm and monitor field devices. Each of the Inputs can be individually configured to send customized emails and notifications when an event is recorded. The device supports a wide variety of protocols it is compatible with over Ethernet. Integration options supported are: 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.

Contact Closure Over Ethernet

The RLH Smart  Input Sensor has the ability to be paired with an RLH Relay Output Device. When using RLH's System Link feature, the two devices become linked establishing a tunnel over an Ethernet network and will transport a digital output signal being received by the Input Sensor through the Ethernet tunnel to the linked Relay Output device. The System Link feature can be set up via: One to One, Many to One, and One to Many allowing for event distribution and consolidation as needed.

View the matching RLH Smart Output Relay


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  (PoE Powering Disabled)
-B Model - 12VDC  (PoE Powering Disabled)

PoE Powered Device:
IEEE 802.3af compliant (Compatible with mode A & B PoE sources)

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
One-To-Many (UDP) < 15ms Many-To-One (TCP) < 250ms *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-IN4-DR-2 Dry: Sourcing Input (100 ohms maximum loop resistance)
SM-IN4-12-2 Wet: Sinking Input (5~15VDC / 5mA)
SM-IN4-48-2 Wet: Sinking Input (20~52VDC / 5mA)

LNK - System Link ON/OFF Status
Inputs - 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 4.93” x W 1.20” x D 3.93” (125mm x 31mm x 100mm)

Mounting Style:
Standard DIN rail (T-35)
Wall mount (with included ears)

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

Limited Lifetime

Contact Closure over Ethernet - One to One (TCP)

Contact Closure over Ethernet - One to One (TCP)

Contact Closure over Ethernet - One to Many (UDP)

Contact Closure over Ethernet - One to Many (UDP)

Event Consolidation - Many Inputs to One Output

Event Consolidation - Many Inputs to One Output

Wet Contact - Integrated Solution

Wet Contact - Integrated Solution


Download the RLH Data Sheet

Download the RLH User GuideDownload MIB File


Smart4 Input Sensor

  • 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

Smart4 Relay Output

  • 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.