Omron NT21-ST121B-E monochrome touchscreen terminal

The Omron reference manual identifies NT21-ST121B-E as the black NT21 monochrome STN touchscreen terminal. The manual records a 260 x 140 dot display, serial communication, and a touch panel for the NT21 model.

Documented system function and position

Rebuilt from individual evidence

The Omron reference manual identifies NT21-ST121B-E as the black NT21 monochrome STN touchscreen terminal.

The manual records a 260 x 140 dot display, serial communication, and a touch panel for the NT21 model.

Sits at the operator panel between the operator and the connected PLC.

Unknown: installed screen project, PLC protocol settings, unit condition, and current commercial availability are not established by the manual.

Exact reference: NT21-ST121B-E
Category: HMI / Display
Evidence checked: 2026-09-12

System role

This section explains what the product does and where it acts in the surrounding system.

Function: Displays PLC-controlled screens and sends touch actions as operator input to the connected PLC.
System position: Sits at the operator panel between the operator and the connected PLC.
Upstream / inputs: Receives screen data and status values from the PLC through the serial link.
Downstream / outputs: Sends touch-switch actions and terminal data to the PLC.
Limitations: Unknown: installed screen project, PLC protocol settings, unit condition, and current commercial availability are not established by the manual.

Evidence ledger

Facts, inferences, and unknowns are kept separate.

Facts

The Omron reference manual identifies NT21-ST121B-E as the black NT21 monochrome STN touchscreen terminal.
Confidence: high
- files.omron.eu — retrieved 2026-09-12; high confidence
The manual records a 260 x 140 dot display, serial communication, and a touch panel for the NT21 model.
Confidence: high
- files.omron.eu — retrieved 2026-09-12; high confidence

Inferences

Inferred system position: Sits at the operator panel between the operator and the connected PLC.
Confidence: medium
Rationale: The documented product function and interfaces establish the adjacent system stages.
- files.omron.eu — retrieved 2026-09-12; high confidence

Unknowns

Unknown: installed screen project, PLC protocol settings, unit condition, and current commercial availability are not established by the manual.
Confidence: low
Missing evidence: installed screen project, PLC protocol settings, unit condition, and current commercial availability are not established by the manual.

System position diagram

A flow from Receives screen data and status values from the PLC through the serial link. through NT21-ST121B-E to Sends touch-switch actions and terminal data to the PLC.. — System position inferred from the captured evidence: Sits at the operator panel between the operator and the connected PLC.

View Mermaid source

flowchart LR
  upstream["Receives screen data and status values from the PLC through the serial link."] -->|"documented input"| item["NT21-ST121B-E"]
  item -->|"documented output"| downstream["Sends touch-switch actions and terminal data to the PLC."]

View diagram labels

Nodes: Receives screen data and status values from the PLC through the serial link.; Omron NT21-ST121B-E monochrome touchscreen terminal; Sends touch-switch actions and terminal data to the PLC.
Edges: Documented upstream interface; Documented downstream interface

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