2.3 Summarize services provided by networked host
📘CompTIA A+ Core 1 (220-1201)
Legacy / Embedded Systems – SCADA
(Supervisory Control and Data Acquisition)
What Are Legacy and Embedded Systems? (Exam Context)
In CompTIA A+, legacy and embedded systems refer to special-purpose computers that:
- Perform one specific function
- Often run older operating systems
- Are designed to run 24/7
- Are not general-purpose PCs
These systems are commonly found in infrastructure environments, and one of the most important examples you must know for the exam is SCADA.
What Is SCADA?
SCADA stands for Supervisory Control and Data Acquisition.
It is a system used to:
- Monitor
- Control
- Collect data from
- Remotely manage
large-scale industrial and infrastructure systems using computers and networks.
📌 Exam definition to remember:
SCADA systems monitor and control physical processes using computers, embedded devices, and network communication.
Why SCADA Is Considered a Legacy / Embedded System
SCADA systems are classified this way because:
- They often use embedded controllers (not PCs)
- Many run legacy operating systems
- They use specialized hardware
- They are designed for reliability, not frequent upgrades
For the exam, you should remember that SCADA is not a modern desktop system — it is a purpose-built control system.
Main Components of a SCADA System
A SCADA system is made up of several IT-based components:
1. Sensors
- Collect raw data from equipment
- Examples of data collected:
- Temperature
- Pressure
- Voltage
- Flow rate
📌 Sensors do not process data — they only detect and send it.
2. RTUs (Remote Terminal Units)
- Embedded devices located near equipment
- Collect data from sensors
- Send data to the control system
- Can receive commands and send them back to equipment
RTUs are:
- Embedded systems
- Low-power
- Designed to work in harsh environments
3. PLCs (Programmable Logic Controllers)
- Special-purpose industrial computers
- Control processes automatically
- Execute logic based on inputs
PLCs are commonly used to:
- Start or stop systems
- Adjust values automatically
- Trigger alerts
📌 For the exam:
PLCs are embedded controllers used in SCADA systems.
4. SCADA Server / Master Station
This is the central control system.
It:
- Receives data from RTUs and PLCs
- Displays information to administrators
- Sends control commands
- Logs events and performance data
This server may run on:
- A dedicated system
- A legacy operating system
- A hardened industrial computer
5. Human-Machine Interface (HMI)
The HMI is the software interface used by IT or system operators.
It allows users to:
- View system status
- Monitor alerts
- Control processes remotely
Examples of HMI functions:
- Dashboards
- Graphs
- Status indicators
- Alarm notifications
📌 For the exam:
HMI allows humans to interact with SCADA systems.
How SCADA Systems Communicate (High Level)
SCADA systems communicate using:
- Ethernet networks
- Serial connections
- Specialized industrial protocols
Key point for A+:
- Communication is often simple, reliable, and slow
- Security was not originally a design priority
Why SCADA Systems Are Important in IT Environments
From an IT perspective, SCADA systems:
- Are part of critical infrastructure
- Must be highly available
- Are difficult to update or replace
- Require careful network management
They are often:
- Isolated from regular office networks
- Protected by firewalls and access controls
- Monitored continuously
Security Concerns (Very Important for the Exam)
SCADA systems have unique security risks:
- Many run outdated operating systems
- Patching is difficult or impossible
- Downtime is not acceptable
- Often lack modern encryption
📌 Exam takeaway:
SCADA systems are high-risk targets and require strong network isolation and monitoring.
Why SCADA Systems Are Still Used
Despite being considered legacy, SCADA systems remain in use because:
- They are stable
- They are proven
- Replacing them is expensive
- Downtime can cause major service disruption
How This Appears on the CompTIA A+ Exam
You may be asked to:
- Identify SCADA as a legacy or embedded system
- Recognize its purpose
- Understand basic components
- Identify security risks
- Know it is used for monitoring and control, not general computing
Key Exam Points to Remember
✔ SCADA = Supervisory Control and Data Acquisition
✔ Used to monitor and control systems remotely
✔ Made of sensors, RTUs, PLCs, servers, and HMI
✔ Considered a legacy / embedded system
✔ Runs continuously
✔ Often uses outdated systems
✔ High security risk
✔ Not a general-purpose computer
