B2J03 — Single-channel serial I/O
Compact remote signal and relay control.
Modbus I/O and RS485 Relay Modules
Choose the module by signal direction, channel count, relay or transistor output, electrical isolation, protocol, supply and enclosure or mounting option.
Modbus I/O Module Product Range
B2J0401 — Analog/digital I/O
Sensor acquisition with PWM-capable outputs.
B2J0405 — Dual-channel transistor output
Two serially controlled transistor channels.
D3J-01xx — Digital input
4–28 digital inputs by model.
D3J-02XX — Relay / transistor output
2–14 isolated outputs by model.
D3J-03xx — Combined digital I/O
Compact mixed input/output stations.
D2J-0701 — Ethernet-to-serial gateway
Related Modbus TCP to Modbus RTU gateway.
Output Modules vs Combined I/O
Input-only stations
Use when switches and sensor states must be collected remotely without local output channels.
RS485 relay output modules
Use when the remote station must switch relay or transistor outputs. D3J-02XX provides 2–14 outputs by model.
Combined I/O and gateways
Use mixed D3J-03xx stations for local input/output. Use D2J-0701 when Ethernet must bridge to a serial network.
Protocol boundary: RS-485 describes the electrical interface; Modbus RTU describes the message protocol. These are non-safety automation modules.
Modbus I/O Module Comparison
| Series | Role | Best-fit task |
|---|---|---|
| B2J03 | Single-channel serial I/O | Compact remote signal and relay control |
| B2J0401 | Analog/digital I/O | Sensor acquisition with PWM-capable outputs |
| B2J0405 | Dual-channel transistor output | Two serially controlled transistor channels |
| D3J-01xx | Digital input | 4–28 digital inputs by model |
| D3J-02XX | Relay / transistor output | 2–14 isolated outputs by model |
| D3J-03xx | Combined digital I/O | Compact mixed input/output stations |
| D2J-0701 | Ethernet-to-serial gateway | Related Modbus TCP to Modbus RTU gateway |
RS485 and Modbus RTU Selection Checklist
Count every signal
Separate inputs, relay outputs, transistor outputs, analog points and pulse-capable channels before selecting a model.
Define the network
Confirm baud rate, addressing, termination, cable length, grounding and whether Ethernet conversion is required.
Confirm mechanics
DIN-rail mounting, bare board and enclosure are ordering options across these ranges; verify the exact supplied format.
Frequently Asked Questions
What is an RS485 relay module?
It is a remote output module whose relay or transistor channels are commanded over an RS-485 link, commonly using Modbus RTU. RS-485 is the physical interface; Modbus is the communication protocol.
Does D3J-02XX provide inputs or outputs?
The D3J-02XX family is treated here according to the confirmed product range: 2–14 isolated outputs depending on model. Its historical URL wording is not a reliable product specification.
Is D2J-0701 an I/O module?
Its primary role is an Ethernet-to-serial gateway. It is listed as a related gateway, not as a substitute for a D3J remote I/O station.
Can Modbus I/O be used in a machine safety circuit?
No. These modules are for ordinary monitoring and automation. Safety functions require components and architectures specifically documented for the required safety performance.