# ANSI/IEEE gas discharge tube symbol

Canonical URL: https://eloragrid.ai/symbols/ansi-gas-discharge-tube
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: GDT
Drawing use: Schematic
Reference families: IEEE / ANSI, Manufacturer

## Symbol convention

Convention: IEEE / ANSI
Form: Autodesk IEEE-oriented protective gas discharge tube form
Autodesk publishes this block under IEEE Symbol Preview: Miscellaneous. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [Gas-discharge protection tube](https://eloragrid.ai/symbols/gas-discharge-protection-tube)

IEEE-oriented protective gas discharge tube: electrodes within a sealed envelope that conduct when voltage exceeds breakdown.

## In plain English

### What does ANSI/IEEE gas discharge tube mean?

A gas discharge tube places protective electrodes inside a sealed gas-filled envelope, giving a more consistent breakdown voltage than an open spark gap. It is widely used on telecom lines, data interfaces and as part of hybrid surge protective devices. The publisher's IEEE miscellaneous preview lists a protective gas discharge tube form.

### A simple example

This illustration is independent and not the IEEE graphic. A GDT responds more slowly than semiconductor clamps and can hold a low on-state voltage, so it is often combined with other elements. The symbol does not show DC sparkover voltage or impulse rating.

### What the drawings help you do

Check DC sparkover and impulse ratings. Look for companion clamp devices in hybrid protection. A gas discharge tube is a sealed gap; an open spark gap is exposed to ambient conditions.

### This particular reference

IEEE-oriented protective gas discharge tube: electrodes within a sealed envelope that conduct when voltage exceeds breakdown. A gas discharge tube is a sealed gap; an open spark gap is exposed to ambient conditions.

### Terms

- DC: Direct current: electricity flowing in one direction.
- 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 IEEE Symbol Preview — Miscellaneous](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-34282BFD-7B8E-48F3-A6ED-93ADBDDDFBD3.htm)
- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/)


## What it represents

A gas discharge tube places protective electrodes inside a sealed gas-filled envelope, giving a more consistent breakdown voltage than an open spark gap. It is widely used on telecom lines, data interfaces and as part of hybrid surge protective devices. The publisher's IEEE miscellaneous preview lists a protective gas discharge tube form.
This illustration is independent and not the IEEE graphic. A GDT responds more slowly than semiconductor clamps and can hold a low on-state voltage, so it is often combined with other elements. The symbol does not show DC sparkover voltage or impulse rating.

## How to read it

- Check DC sparkover and impulse ratings.
- Look for companion clamp devices in hybrid protection.

## Information to show or reference

- State sparkover voltage.
- Show earth connection.
- Identify hybrid protection stages.

## Important distinction

A gas discharge tube is a sealed gap; an open spark gap is exposed to ambient conditions.

## Facts

- Convention evidence: Autodesk IEEE Symbol Preview: Miscellaneous (Protective Gas Discharge Tube)
- Public vendor block name: HFU1_S00374 (Autodesk identifier; not an IEEE symbol number)
- Standards context: IEEE/ANSI 315-1975 covers diagram graphics; IEEE lists this edition as Inactive-Reserved.
- Preview: Original educational illustration; consult the publisher and applicable standard for the exact graphic

## Public references

- [Autodesk IEEE Symbol Preview — Miscellaneous](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-34282BFD-7B8E-48F3-A6ED-93ADBDDDFBD3.htm) — Autodesk. Exact public IEEE-oriented category page listing the protective gas discharge tube form.
- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/) — IEEE Standards Association. Graphic-symbol standards context and official status; not a source of reproduced artwork.

## 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.