# Tap-position coded-input decoder

Canonical URL: https://eloragrid.ai/symbols/tap-position-coded-input-decoder
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: TCD
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: substations
Input: Tap contact code
Output: Decoded tap position

Converts the installed tap-position contact code into the controller's displayed position.

## In plain English

### What this block does

Converts the installed tap-position contact code into the controller's displayed position.

### A simple example

In a substation, a voltage regulator can request a tap change and check the resulting tap-position feedback. A separate controller stages cooling equipment according to the transformer manufacturer's defined conditions. For this reference, the drawing identifies “Tap contact code” at the input and “Decoded tap position” at the output. Invalid codes require explicit handling.

### What the drawings help you do

Start at the named input: Tap contact code. Identify its source device or document and the state represented on the drawing. Follow the named output: Decoded tap position. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Tap contact code
- Output: Decoded tap position
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Tap contact code → TCD → Decoded tap position
A reading guide. The entry's original illustration and input/output facts describe this application.

- [SEL-2414 transformer monitor](https://selinc.com/products/2414/)


## What it represents

Converts the installed tap-position contact code into the controller's displayed position. Transformer regulation changes the selected winding connection to influence voltage, while cooling control manages the installed fans and pumps. Commands, mechanical position and measured results belong to different parts of the diagram.
In a substation, a voltage regulator can request a tap change and check the resulting tap-position feedback. A separate controller stages cooling equipment according to the transformer manufacturer's defined conditions. For this reference, the drawing identifies “Tap contact code” at the input and “Decoded tap position” at the output. Invalid codes require explicit handling.
Keep tap-change permission, limit contacts, movement indication and measured voltage distinct. Actual tap positions, time delays, cooling ratings and allowable parallel operation require the selected transformer control design. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.

## How to read it

- Start at the named input: Tap contact code. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Decoded tap position. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Invalid codes require explicit handling.
- Keep tap-change permission, limit contacts, movement indication and measured voltage distinct. Actual tap positions, time delays, cooling ratings and allowable parallel operation require the selected transformer control design.

## Information to show or reference

- Label the source and connection reference for tap contact code.
- Identify the destination and defined state of decoded tap position.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Invalid codes require explicit handling.

## Important distinction

Invalid codes require explicit handling. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

## Facts

- Representation: Functional block
- Installation focus: Substations
- Input / boundary: Tap contact code
- Output / connection: Decoded tap position
- Lookup label: TCD is a library lookup label, not a standard device designation.

## Public references

- [SEL-2414 transformer monitor](https://selinc.com/products/2414/) — SEL. Public technical context for transformer regulation and cooling control. Transformer temperature, cooling, tap changing and parallel operation. The application text and educational graphic are independently authored; the publisher does not certify this representation.

## 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.