Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

HYST

IEC

IEC hysteresis (bi-threshold) qualifier

The hysteresis mark, a small loop drawn with two offset steps, appears either as a general qualifier for a Schmitt-trigger element or next to a single input to show that input has two thresholds. TI's public overview lists both uses.

Drawing use

Schematic

Application

Logic & signals

Reference family

IEC / Manufacturer

Form evidence

Hysteresis loop mark inside the outline or at an input. Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier.

A distinction that matters

A drawn square-wave inside a G element indicates an astable, not hysteresis.

Full referenceAdd to legend

1

IEC

IEC Schmitt-trigger buffer (rectangular form)

A Schmitt-trigger buffer is an IEC 1 element with the hysteresis qualifier drawn inside the box. The qualifier states that the input has two thresholds, one for a rising signal and one for a falling signal, so the output does not chatter when the input passes slowly through the switching region.

Drawing use

Schematic

Application

Logic & signals

Reference family

IEC / Manufacturer

Form evidence

1 element with the hysteresis qualifier inside the outline. Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.

A distinction that matters

A plain 1 buffer has a single threshold; only the hysteresis mark indicates Schmitt behaviour.

Full referenceAdd to legend

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