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A curved-back shield with a second arc and an output bubble.
Also known as: Equivalence gate, Exclusive NOR gate, XNOR, Shield with a bubble
The XNOR gate outputs true when its inputs match, which makes it the equality detector of digital logic — a row of them is how a comparator circuit checks two numbers for equality. It is an XOR with an inverting bubble on the output.
Denotes a gate whose output is true when its inputs are equal.
Contexts: Electrical equipment
Is drawn as the XOR shield with a small circle added at the output, the circle being the general inversion mark.
Contexts: Electrical equipment
Is the building block of equality comparison: an array of XNOR gates feeding an AND gate tests two binary words for identity.
Contexts: Electrical equipment
Appears as a rectangle marked '=' in the IEC 60617 rectangular scheme rather than as a shield.
Contexts: Electrical equipment
A shield shape with a curved left edge and a pointed right end, a second arc outside the left edge, and a small circle touching the point.