# ANSI/IEEE Symmetric gas discharge tube form Canonical URL: https://eloragrid.ai/symbols/ansi-symmetric-gas-discharge-tube Publisher: Elora Grid Updated: 2026-10-28 Lookup label: F Drawing use: Schematic Reference families: IEEE / ANSI, Manufacturer ## Symbol convention Convention: IEEE / ANSI Form: Protective Gas Discharge Tube, Symmetric Autodesk IEEE Symbol Preview: Miscellaneous, block HFU1_S00375. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier. Related representation: [Symmetric gas discharge tube](https://eloragrid.ai/symbols/iec-symmetric-gas-discharge-tube) IEEE-library form of symmetric gas discharge tube: a protective gas discharge tube drawn with identical electrodes either side, listed as a distinct symmetric form. ## In plain English ### What does ANSI/IEEE Symmetric gas discharge tube form mean? This reference locates symmetric gas discharge tube in Autodesk's IEEE-oriented miscellaneous family. The publisher's IEC-oriented library lists a symmetric protective gas discharge tube separately from the standard form. The symmetric drawing presents both electrodes identically, emphasising that the device behaves the same for either polarity of surge, as is typical for AC and signal line protection. The public library uses HFU1_S00375 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number. ### A simple example Use the surrounding circuit labels and the project legend to identify the intended operating condition and connection. Carry the same device reference into the schedule or equipment document so the symbol can be reconciled with its real terminals, function and operating limits. ### What the drawings help you do The symbol is a drawing variant and does not establish electrical ratings. Breakdown voltage, impulse current and follow current behaviour come from the product data. Readers should not infer three-terminal construction from this form; three-electrode tubes need their own representation. Read ratings from the product data, not the symbol. The symmetric form draws identical electrodes; the standard gas discharge tube form may show the electrodes differently. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted. ### This particular reference IEEE-library form of symmetric gas discharge tube: a protective gas discharge tube drawn with identical electrodes either side, listed as a distinct symmetric form. The symmetric form draws identical electrodes; the standard gas discharge tube form may show the electrodes differently. ### Terms - AC: Alternating current: electricity whose direction changes periodically. - Terminal: An identified point where a conductor connects. - Signal: Electrical information passed between devices, rather than necessarily the main power supply. 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) ## What it represents This reference locates symmetric gas discharge tube in Autodesk's IEEE-oriented miscellaneous family. The publisher's IEC-oriented library lists a symmetric protective gas discharge tube separately from the standard form. The symmetric drawing presents both electrodes identically, emphasising that the device behaves the same for either polarity of surge, as is typical for AC and signal line protection. The public library uses HFU1_S00375 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number. Use the surrounding circuit labels and the project legend to identify the intended operating condition and connection. Carry the same device reference into the schedule or equipment document so the symbol can be reconciled with its real terminals, function and operating limits. The symbol is a drawing variant and does not establish electrical ratings. Breakdown voltage, impulse current and follow current behaviour come from the product data. Readers should not infer three-terminal construction from this form; three-electrode tubes need their own representation. Read ratings from the product data, not the symbol. The symmetric form draws identical electrodes; the standard gas discharge tube form may show the electrodes differently. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted. ## How to read it - Read ratings from the product data, not the symbol. - Check whether a three-electrode tube is intended instead. ## Information to show or reference - State sparkover voltage and impulse rating. - Show the earth or return side. - Keep the form consistent with the legend. ## Important distinction The symmetric form draws identical electrodes; the standard gas discharge tube form may show the electrodes differently. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Miscellaneous; published form: Protective Gas Discharge Tube, Symmetric. - Public vendor block: HFU1_S00375. Vendor library token, not an IEEE symbol number. - Graphic cue: Sealed envelope with matching electrodes either side - Publisher form: Protective Gas Discharge Tube, Symmetric (HFU1_S00375 Autodesk identifier) - Preview: Original educational illustration; consult the publisher and applicable standard for the exact graphic - Artwork scope: Original educational geometry. Exact standard graphics, product ratings and terminal pinouts are not certified. ## 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. Public IEEE-oriented Miscellaneous table explicitly lists HFU1_S00375 as Protective Gas Discharge Tube, Symmetric. This supports the vendor convention context, not reproduction of the publisher graphic. ## 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.