# Motor-operated disconnector limit switch interface

Canonical URL: https://eloragrid.ai/symbols/motor-operated-disconnector-limit-switch-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: MDLSI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchyards
Input: Drive end-position contacts
Output: Open and closed position inputs

Carries the selected mechanism's end-position contacts into the yard control circuit.

## In plain English

### What this block does

Carries the selected mechanism's end-position contacts into the yard control circuit.

### A simple example

In a switchyard bay, a bus selector can use a different physical construction from a line disconnector. Each device still needs an identified operating mechanism, position indication and interlocking interface. For this reference, the drawing identifies “Drive end-position contacts” at the input and “Open and closed position inputs” at the output. Motor-stop limits and indication contacts may differ.

### What the drawings help you do

Start at the named input: Drive end-position contacts. Identify its source device or document and the state represented on the drawing. Follow the named output: Open and closed position inputs. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Drive end-position contacts
- Output: Open and closed position inputs
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Drive end-position contacts → MDLSI → Open and closed position inputs
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Disconnectors and earthing switches](https://www.siemens-energy.com/global/en/home/products-services/product-offerings/disconnectors-earthing-switches.html)


## What it represents

Carries the selected mechanism's end-position contacts into the yard control circuit. Disconnector and earthing references identify different mechanical constructions and connection duties within a yard. The primary diagram shows which conductors are joined or earthed; the equipment drawing explains how its contacts and supports move.
In a switchyard bay, a bus selector can use a different physical construction from a line disconnector. Each device still needs an identified operating mechanism, position indication and interlocking interface. For this reference, the drawing identifies “Drive end-position contacts” at the input and “Open and closed position inputs” at the output. Motor-stop limits and indication contacts may differ.
The construction name does not establish load-breaking capability, short-circuit making duty or operating permission. Verify these properties in the selected equipment data and the station interlocking scheme. 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: Drive end-position contacts. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Open and closed position inputs. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Motor-stop limits and indication contacts may differ.
- The construction name does not establish load-breaking capability, short-circuit making duty or operating permission. Verify these properties in the selected equipment data and the station interlocking scheme.

## Information to show or reference

- Label the source and connection reference for drive end-position contacts.
- Identify the destination and defined state of open and closed position inputs.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Motor-stop limits and indication contacts may differ.

## Important distinction

Motor-stop limits and indication contacts may differ. 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: Switchyards
- Input / boundary: Drive end-position contacts
- Output / connection: Open and closed position inputs
- Lookup label: MDLSI is a library lookup label, not a standard device designation.

## Public references

- [Disconnectors and earthing switches](https://www.siemens-energy.com/global/en/home/products-services/product-offerings/disconnectors-earthing-switches.html) — Siemens Energy. Public technical context for disconnector and earthing applications. Disconnector construction, earthing switches and operating mechanisms. 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.