The symbols printed on rating plates, switches and power supplies: which power state a control selects, whether a terminal expects alternating or direct current, and how the appliance protects against electric shock. Several pairs are near-identical by design and mean materially different things — a broken circle versus a closed one, a double square versus an earth terminal.
A vertical bar (|) — IEC 60417-5007, marking the control position that places equipment into a fully powered state.
A plain circle (◯) — IEC 60417-5008, marking the control position that disconnects power from the equipment.
A vertical line entering the top of a broken circle — IEC 60417-5009, marking a control that puts equipment into a low-power state rather than fully disconnecting it.
A vertical line inside an unbroken circle — IEC 60417-5010, marking a button that switches equipment between fully on and fully off.
A wavy line (∼) — IEC 60417-5032, indicating on a rating plate that equipment is suitable for alternating current.
A solid line above a dashed line — IEC 60417-5031, indicating on a rating plate that equipment is suitable for direct current.
A circle enclosing a three-bar earth glyph — IEC 60417-5019, marking the protective earth (ground) terminal on Class I equipment.
A small square inside a larger square — IEC 60417-5172, marking equipment protected by double or reinforced insulation rather than an earth connection.