Manual call point (MAC)

Offshore F&G layout practice (ISA 5.1-style letter codes) / ISO 7240 / NFPA 72 / ISO 7240-11

Drawn as

A square with a smaller filled circle inside (the break-glass button), sometimes marked MAC or MCP.

Meaning

Manual alarm call point. Pressing it raises a fire alarm (and on many platforms initiates ESD or GA). Becomes manual-call-point. ESD push-buttons look similar but are marked ESD.

Variants

Yellow (ESD) vs red (fire) call points are only told apart by text or colour
NFPA-style legends: a small rectangle with "F" or "MS" (manual station)