Product Overview
ICP DAS tM-SG4 CR RS-485 Termination Resistor Module – Unused NOS
You're looking at an ICP DAS tM-SG4 CR — a DIN-rail-mounted RS-485 signal conditioning module designed to stabilize long or noise-prone serial networks through adjustable termination and biasing.
This is not a protocol device and not a gateway. It exists for one purpose: to make RS-485 behave when cable length, impedance mismatch, or idle-line instability start to erode signal integrity.
Product Condition
Unused, New Old Stock. The module was never installed or placed into service.
Product Overview
The tM-SG4 CR connects in parallel with an RS-485 bus and provides switch-selectable pull-up, pull-down, and termination resistors. This allows engineers and technicians to tune line bias and impedance rather than relying on a fixed 120 ohm terminator.
It is intended for RS-485 networks longer than 100 meters or installations where waveform quality must be verified and adjusted, typically at one or both physical ends of the bus.
Key Features
- ICP DAS tM-SG4 CR RS-485 termination and bias module
- Designed for long-distance RS-485 networks over 100 meters
- 15-step switch-selectable termination resistor
- Termination range approximately 65 ohm to 560 ohm
- Selectable pull-up and pull-down resistors for line biasing
- Pull-up and pull-down options: 1 kΩ, 10 kΩ, or 100 kΩ
- Parallel connection to DATA+ and DATA− lines
- 10–30 VDC powered module with status indicators
- DIN-rail mount housing suitable for control cabinets
Applications
- RS-485 networks with long cable runs
- Industrial Modbus RTU installations
- Noise-prone factory or plant environments
- Control panels requiring adjustable bus termination
- Commissioning and troubleshooting RS-485 systems
- Automation training and bench evaluation setups
Frequently Asked Questions
Does this module implement any communication protocol?
No. The tM-SG4 CR is a passive signal-conditioning accessory. It does not process data or implement protocols such as Modbus.
Why use adjustable termination instead of a fixed 120 ohm resistor?
Cable impedance, topology, and installation conditions vary. Adjustable termination allows the user to reduce reflections and ringing by matching the line more closely.
Where should this module be installed on the bus?
It is typically installed at one or both physical ends of an RS-485 trunk, depending on network design.
What do the pull-up and pull-down resistors do?
They bias the RS-485 lines to a known idle state when no driver is active, preventing floating inputs and false transitions.
Is this module a replacement for proper cabling practices?
No. Correct twisted-pair cabling, bus topology, and grounding are still required for reliable RS-485 operation.
When the network gets long and the edges get messy, this module gives you the knobs engineers wish every RS-485 install had from the start.
