Wire Junction / Node Symbol
Definition: The Wire Junction / Node symbol represents the point at which two or more conductors are electrically connected in a circuit diagram, depicted as a filled dot at the intersection of crossing or meeting wires, as specified in IEC 60617-02 and ANSI Y32.2/IEEE 315 to unambiguously indicate that the wires share the same electrical net.
Also known as: junction dot, node dot, wire node, connection dot, solder dot, T-junction, wire tee.
What the Wire Junction / Node symbol means
The Wire Junction / Node symbol is the filled-dot indicator placed at wire intersections to confirm electrical connectivity. Without this dot, two crossing lines could be interpreted as either connected or merely crossing (passing each other without connection). The junction dot removes all ambiguity: wherever it appears, all wires meeting at that point belong to the same net and carry the same potential.
In circuit diagrams the junction symbol has four terminals—Top, Right, Bottom, and Left—representing conductors arriving from all four orthogonal directions. A T-junction (three wires meeting) requires the same filled dot; an X-junction (four wires meeting) should be used only with a dot to avoid confusion with a no-connection crossing, or better, avoided by rerouting wires to form two separate T-junctions.
How to identify the Wire Junction / Node symbol
The symbol is a filled (solid) circular dot placed precisely at the point where two or more wire lines intersect or meet. The dot diameter is typically 1.5–3 times the wire line width to be clearly visible. A dot at a T-intersection confirms connection; a dot at an X-intersection confirms that all four wires share one node. Absence of a dot at an intersection means no connection per IEC 60617-02 modern convention.
Function in a circuit
The wire junction node is a purely diagrammatic element that establishes net topology in a schematic. In EDA software (KiCad, Altium, Eagle, OrCAD) the junction symbol creates a netlist connection between all wires meeting at that point; omitting the junction where wires should connect will cause the ERC to flag an unconnected wire error or, worse, generate an incorrect netlist that creates a PCB short circuit or open circuit.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-02 (graphical symbols for diagrams: symbol elements and qualifying symbols) defines the filled-dot junction symbol and specifies the rule: a dot at an intersection means connection; no dot at a crossing means no connection. This convention is unambiguous and is the current international standard. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2-1975 (R1989) and IEEE 315-1975 specify the same filled-dot convention for connections; older US drawings also used the hump/arc bridge for no-connection crossings, but the modern ANSI/IEEE standard relies solely on the dot convention. |
| Key difference | IEC 60617-02 and ANSI Y32.2/IEEE 315 use identical filled-dot junction symbols. The only difference is historical: older ANSI drawings also used a hump on one crossing wire for no-connection, while IEC never used the hump. Modern practice under both standards uses only the dot to indicate connection. |
Terminals / pins
| Pin | Name |
|---|---|
| top | Top |
| right | Right |
| bottom | Bottom |
| left | Left |
Typical values
The wire junction symbol has no electrical values; it is a topological indicator establishing net connectivity at the intersection point.
Where the Wire Junction / Node symbol is used
- Any schematic diagram where a branch wire tees off a main signal or power line
- Digital logic schematics where bus signals fan out to multiple gate inputs from a single driver output
- Power distribution diagrams showing multiple loads connected in parallel to the same supply rail
- PCB schematic capture (KiCad, Altium, Eagle) where junction nodes must be explicit for correct netlist generation
- Ladder logic diagrams in PLC programming where rungs share common power rail connections
- Relay control diagrams where multiple relay coil or contact circuits branch from the same control bus
Example
In a 24 V DC power distribution schematic, the +24 V supply rail runs horizontally across the diagram; each vertical branch to a relay coil, solenoid, or sensor is connected with a wire-junction dot, confirming that all branch wires share the same +24 V net and are not merely crossing the power rail without connection.
Key facts
- The Wire Junction / Node symbol has four terminals: Top, Right, Bottom, and Left, representing conductors that may arrive from any of the four orthogonal directions.
- The symbol is a filled circular dot placed at the exact intersection point; in IEC 60617-02 and IEEE 315, a dot means connection and the absence of a dot at a crossing means no connection.
- Omitting a junction dot where wires should be connected is one of the most common schematic errors; it causes ERC failures in EDA tools and can result in incorrect PCB netlists.
- A four-wire X-junction should be avoided in professional schematics; it is better to use two T-junctions offset slightly, or to re-route one wire to avoid the X-crossing and use a T-junction instead.
- The junction dot size should be 1.5–3× the line width to be clearly visible at the diagram's printed or displayed scale; too-small dots are a common readability problem.
- In EDA tools such as KiCad 6+, adding a junction symbol is required when wires meet at a T or X intersection; the tool does not automatically create connections at intersections without the junction symbol.
- The wire junction node carries no voltage drop, resistance, or impedance; it is a zero-impedance node connecting all conductors at that point to the same electrical potential.
Frequently asked questions
What does the wire junction symbol mean in a circuit diagram?
The wire junction symbol—a filled dot at a wire intersection—means that all wires meeting at that point are electrically connected and share the same net (same potential). It is the definitive indicator of connection in schematic diagrams per IEC 60617-02 and IEEE 315.
What does the wire junction node symbol look like?
The wire junction node is a small filled (solid) circular dot placed at the exact point where two or more wires intersect or meet. The dot is typically 1.5–3 times the wire line width. Its presence at an intersection unambiguously means connection; its absence means no connection.
What is the IEC vs ANSI difference for wire junction symbols?
Both IEC 60617-02 and ANSI Y32.2/IEEE 315 use the identical filled-dot symbol to indicate wire connections. There is no glyph difference. The historical difference was in the no-connection symbol: older ANSI used a hump arc, while IEC never did. Modern drawings under both standards use only the dot for connection.
What happens if I forget the junction dot in a schematic?
If a junction dot is omitted where wires should be connected, most EDA tools will treat the wires as crossing without connection, creating an incorrect netlist. This can result in open circuits or missing connections on the PCB. The ERC (electrical rules check) will typically flag the intersection as an error.
What is the designator or reference for a wire junction in a schematic?
Wire junctions have no designator letter or reference number—they are net topology symbols, not components. They do not appear in the bill of materials and carry no component value.
How do I indicate that two crossing wires are NOT connected in a schematic?
Simply draw the crossing lines without a filled dot at the intersection. Per IEC 60617-02 and IEEE 315, a plain cross with no dot means no connection. In older ANSI drawings a small arc (hump) on one wire also indicated no connection, but this convention is deprecated in modern practice.
What standard defines the wire junction dot symbol?
IEC 60617-02 (graphical symbols for diagrams) defines the filled-dot connection symbol. ANSI Y32.2-1975 (R1989) and IEEE 315-1975 specify the same convention for North American drawings. Both standards apply the same rule: dot at intersection = connected; no dot = not connected.
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