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

OL NO

Symbols

Motor overload alarm NO contact

An overload alarm NO contact closes on the documented overload relay operation. The schematic identifies the alarm or feedback path independently of the motor-stopping contact.

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

A distinction that matters

A trip alarm contact is different from a contactor position indication contact.

Full reference

Symbols

Normally open contact

A normally open contact is open in the normal state defined for the device. Operating its relay, pushbutton or other parent device may close the contact. The meaning of normal must be established from the drawing convention and equipment documentation; it is not necessarily the current live condition of the installation.

Drawing use: Schematic
Application: Control circuits
Reference family: IEC / IEEE / ANSI

A distinction that matters

Normally open describes the stated normal condition. A position indication or operating snapshot may use a different state convention.

Full reference

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