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.

First referenceCompare with

IEC

Photoelectric light switch plan mark

A photoelectric switch, or photocell, measures ambient light and operates a lighting circuit at a set lux threshold. Plans draw a small switch or box with inward arrows to indicate light received, placed where the cell can see the sky without seeing the luminaires it controls.

Drawing use: GA
Application: Installation & communications
Reference family: IEC
Form evidence: Light-sensitive switch. IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.

A distinction that matters

A light-dependent resistor is a component; a photoelectric switch is a complete lighting control device on the plan.

Full reference

LDR

Symbols

Light-dependent resistor

A light-dependent resistor changes resistance according to illumination. The schematic places the sensing element in its actual electrical network and the equipment detail identifies the illumination conditions.

Drawing use: SLD / Schematic
Application: Control circuits
Reference family: IEC / Manufacturer

A distinction that matters

An LDR changes resistance; a photodiode produces a different semiconductor sensing response.

Full reference

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