An electrical resistor.
In a circuit diagram, a circle with a cross inside it typically represents a battery or a cell. The cross indicates the positive terminal, while the surrounding circle represents the overall component. This symbol is commonly used to denote the source of electrical energy in a circuit.
Not oak in the inside circle , not wood in the small circle
Not stop sign in the inside circle , not red in the small circle
Not stop sign in the inside circle , not red in the small circle
Figure B. equilateral triangle (small circle) inside of isosceles triangle (big cirlce)
A Venn diagram with a large circle representing all dogs with a smaller circle inside that circle representing poodles.
bird circle inside the animal circle
has wings in outer circle (*bigger circle) insect inside inner circle (*smaller circle)
A circle labeled "metal" with a smaller circle labeled "aluminum" completely inside it
The universal set of a Venn diagram is the rectangle and everything that is inside it.
Ceiling pull switch on an electrical diagram--see link
A circle with a small cross inside represents a port on a map.