NO
Normally open contact
A contact shown open in the normal state defined for its device.
Schematic
Electrical symbols.
Explore electrical symbols, functional blocks and circuit arrangements for switchgear, switchrooms, substations, switchyards and microgrids. Detailed explanations, drawing notes, public sources and original SVG/DXF illustrations.
Control circuits
NC
Normally closed contact
A contact shown closed in the normal state defined for its device.
Schematic
CO
Changeover contact
A contact arrangement switching a common connection between two contact paths.
Schematic
Coil
Relay coil
The operating element associated with a relay and its separately drawn contacts.
Schematic
KM
Contactor
An electrically operated switching device commonly used for repeated switching duties.
SLD / Schematic
PB NO
Normally open pushbutton
A pushbutton contact normally shown open before actuation.
Schematic
PB NC
Normally closed pushbutton
A pushbutton contact normally shown closed before actuation.
Schematic
E-stop
Emergency-stop operator
An identified emergency-stop operator and its documented contact arrangement.
Schematic
SS
Selector switch
An operator switch selecting between documented control positions.
Schematic
Lamp
Indicator lamp
A visual indicator associated with a documented control or equipment condition.
Schematic
PLC I/O
PLC input / output
A controller interface point connecting field signals to an identified module channel.
Schematic
R
Resistor
A resistive component with its value and purpose documented separately.
Schematic
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Read the drawing, not just the mark
Small details. Different meanings.
Understand symbols, equipment tags and function numbers—and know when a generic object needs a manufacturer drawing.
In plain English
What do electrical symbols tell you?
Electrical symbols are shorthand for equipment, functions and connections. They let you follow how a circuit works without drawing every physical detail.
A simple example
On a microgrid single-line diagram, a current-transformer symbol marks a measurement point and a breaker symbol marks where a circuit can be disconnected. Their labels identify the actual equipment.
What the drawings help you do
Follow the connected lines to trace power or control signals. Use the project legend to interpret symbols and the selected manufacturer's drawings for dimensions and terminal connections.
- Single-line diagram
- A simplified power-system drawing that often uses one line to represent a three-phase circuit.
- Legend
- The key explaining a drawing's symbols and labels.