---
title: "PLC (Programmable Logic Controller)"
description: "A PLC (Programmable Logic Controller) is a ruggedised industrial computer running programmed control logic, designed for long-life unattended operation in harsh industrial environments. PLCs are the standard control device for most discrete and sequential process-equipment functions, including sonic-horn cycle sequencing."
canonical_url: "https://sylio.co/glossary/plc"
last_updated: "2026-06-28T02:29:28.755Z"
---

A **PLC (Programmable Logic Controller)** is a ruggedised industrial computer running programmed control logic, designed for long-life unattended operation in harsh industrial environments. PLCs are the standard control device for most discrete and sequential process-equipment functions, including [sonic-horn](/glossary/sonic-horn) cycle sequencing.

## Sonic-horn / PLC integration patterns

- **Dedicated horn PLC** — a small PLC running only the [cycle-controller logic](/glossary/cycle-controller-sequencer); simple, easy to commission, isolated from plant-DCS changes
- **Plant-PLC integration** — sonic-horn sequencing as a subroutine inside an existing plant PLC; allows tighter operator interaction and DCS visibility
- **Hybrid** — dedicated PLC for the cleaning system with a fieldbus link ([Modbus](/glossary/modbus-profibus-profinet) or similar) to the plant control system

## Procurement implications

Specifying the PLC integration approach early in the project saves substantial commissioning time. Plants that defer the decision until installation often discover that retrofit integration requires more DCS configuration time than the entire horn-installation work.

## Related terms

- [DCS (Distributed Control System)](/glossary/dcs)
- [Cycle controller / sequencer](/glossary/cycle-controller-sequencer)
- [Modbus / Profibus / Profinet](/glossary/modbus-profibus-profinet)