# Screened twisted pair

Canonical URL: https://eloragrid.ai/symbols/iec-screened-twisted-pair
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: W
Drawing use: Schematic
Reference families: IEC

## Symbol convention

Convention: IEC
Form: Twisted pair with individual screen
Independent combination of IEC-context twisted-pair and screen forms; not certified IEC geometry.

Two conductors drawn twisted together inside a screen outline, as used for noise-sensitive signal and communication pairs.

## In plain English

### What does Screened twisted pair mean?

The screened twisted pair combines two separate protections against interference. Twisting cancels magnetically induced voltage between the two cores, and the screen intercepts capacitive coupling from nearby power conductors. The form is typical for RS-485 links, 4 to 20 mA loops in noisy plant and resolver or encoder feedback pairs.

### A simple example

On a drawing each screened pair should be identifiable in the core allocation, because a multipair cable may contain several of them plus an overall screen. The symbol does not tell you the characteristic impedance or twist rate, which matter for data networks and must come from the cable specification.

### What the drawings help you do

Confirm the pair belongs to the circuit it is drawn on, not split across two circuits. Check how the pair screen is terminated relative to any overall screen. A screened twisted pair adds a shield; the plain twisted-pair indication shows twisting only and no screen.

### This particular reference

Two conductors drawn twisted together inside a screen outline, as used for noise-sensitive signal and communication pairs. A screened twisted pair adds a shield; the plain twisted-pair indication shows twisting only and no screen.

### Terms

- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Autodesk IEC-60617 preview: Cable identification and twisted-pair annotation](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-37A08C35-43A3-484D-B0EB-0BBCBC4BE709.htm)
- [IEC-60617 symbol preview directory](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-7871E6EF-24D5-467E-9B74-321FEDC9DFDA.htm)


## What it represents

The screened twisted pair combines two separate protections against interference. Twisting cancels magnetically induced voltage between the two cores, and the screen intercepts capacitive coupling from nearby power conductors. The form is typical for RS-485 links, 4 to 20 mA loops in noisy plant and resolver or encoder feedback pairs.
On a drawing each screened pair should be identifiable in the core allocation, because a multipair cable may contain several of them plus an overall screen. The symbol does not tell you the characteristic impedance or twist rate, which matter for data networks and must come from the cable specification.

## How to read it

- Confirm the pair belongs to the circuit it is drawn on, not split across two circuits.
- Check how the pair screen is terminated relative to any overall screen.

## Information to show or reference

- Allocate both cores of the pair to one signal circuit.
- Show the pair screen termination.
- Record cable impedance for data circuits.

## Important distinction

A screened twisted pair adds a shield; the plain twisted-pair indication shows twisting only and no screen.

## Facts

- Graphic cue: Crossed or twisted pair of lines inside a screen outline
- Typical use: Serial data, analogue loops and feedback devices
- Preview: Original educational illustration; consult the publisher and applicable standard for the exact graphic

## Public references

- [Autodesk IEC-60617 preview: Cable identification and twisted-pair annotation](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-37A08C35-43A3-484D-B0EB-0BBCBC4BE709.htm) — Autodesk. Public IEC-60617 preview family that includes the twisted-pair marker.
- [IEC-60617 symbol preview directory](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-7871E6EF-24D5-467E-9B74-321FEDC9DFDA.htm) — Autodesk. Public directory of IEC-oriented symbol families.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.