Side-by-side reference

Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

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Symbols

Lightning protection test joint

Each down-conductor usually has a test joint at a convenient height above ground. Opening it separates the above-ground lightning conductor from the earth electrode, so electrode resistance and conductor continuity can be measured. Elevations show it as a small box or clamp mark on the down-conductor.

Drawing use: GA / Schematic
Application: Connections & wiring
Reference family: IEC / IEEE / ANSI

A distinction that matters

A lightning test joint separates the down-conductor from its electrode; an earth test link separates the installation MET from its electrode.

Full reference

Symbols

Lightning protection down-conductor

Down-conductors run from the air termination network on the roof to the earth electrodes, carrying lightning current by the shortest practical path. Installation guidance describes them as part of the building protection system together with the capture device and earth leads. Elevations and roof plans show them as a distinct line style.

Drawing use: GA / Schematic
Application: Connections & wiring
Reference family: IEC / IEEE / ANSI

A distinction that matters

A down-conductor carries lightning current to earth; a protective earth conductor carries fault current from the electrical installation.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.