# IEC transparent D latch (rectangular form)

Canonical URL: https://eloragrid.ai/symbols/iec-d-latch
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: C1 1D
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular bistable with static C1 and 1D inputs
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.
Related representation: [Transparent D latch](https://eloragrid.ai/symbols/transparent-d-latch)

IEC bistable with a static C1 control and 1D input; the output follows D while C1 is active.

## In plain English

### What does IEC transparent D latch (rectangular form) mean?

The transparent latch is drawn like the D flip-flop but the C1 input has no dynamic wedge. While C1 is at its internal 1 state, the output follows the 1D input; when C1 returns to 0 the last value is held. TI's overview describes this as a level-operated control input.

### A simple example

Latches are used to capture data from a bus or to hold a value for a display or relay driver. In octal devices the common-control block carries C1 and the output enable, with eight per-bit elements below.

### What the drawings help you do

Because the output follows the input during the active level, glitches on D during that time pass through. The symbol shows this behaviour only through the absence of the wedge, so check it carefully.

### This particular reference

IEC bistable with a static C1 control and 1D input; the output follows D while C1 is active. The IEC D flip-flop has a dynamic wedge on C1 and captures only at the edge.

### Terms

- Normally open / normally closed: The contact state in the normal condition defined for the drawing.
- Coil: A wound conductor that can produce a magnetic field when energised.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf)
- [SN74HC373 — transparent D latches](https://www.ti.com/lit/ds/symlink/sn74hc373.pdf)


## What it represents

The transparent latch is drawn like the D flip-flop but the C1 input has no dynamic wedge. While C1 is at its internal 1 state, the output follows the 1D input; when C1 returns to 0 the last value is held. TI's overview describes this as a level-operated control input.
Latches are used to capture data from a bus or to hold a value for a display or relay driver. In octal devices the common-control block carries C1 and the output enable, with eight per-bit elements below.
Because the output follows the input during the active level, glitches on D during that time pass through. The symbol shows this behaviour only through the absence of the wedge, so check it carefully.

## How to read it

- No wedge on C1 means level-sensitive.
- In octal parts, look for C1 in the common-control block.

## Information to show or reference

- Draw C1 without a dynamic mark.
- Prefix the data input with 1.
- Show output enable separately if present.

## Important distinction

The IEC D flip-flop has a dynamic wedge on C1 and captures only at the edge.

## Facts

- Clock type: Level-operated
- Key labels: C1, 1D
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Transparent latch behaviour with level-operated control input.
- [SN74HC373 — transparent D latches](https://www.ti.com/lit/ds/symlink/sn74hc373.pdf) — Texas Instruments. Transparent latch documentation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.