CCST CCST Communications & Networking in Control Systems 1 — Questions and Answers
Question 1: Which industrial communication protocol uses a token-passing bus architecture and is commonly found in legacy process control systems?
- PROFIBUS DP (Correct answer)
- Modbus RTU
- HART
- Foundation Fieldbus
Correct answer: PROFIBUS DP
PROFIBUS DP uses a token-passing bus architecture that allows deterministic communication in process automation environments.
Question 2: What is the primary purpose of the HART (Highway Addressable Remote Transducer) protocol in process control?
- High-speed data transfer between PLCs
- Simultaneous analog and digital communication over the same two-wire loop (Correct answer)
- Wireless sensor communication
- Ethernet-based control networking
Correct answer: Simultaneous analog and digital communication over the same two-wire loop
HART overlays digital signals on a standard 4–20 mA analog loop, enabling simultaneous analog process variable transmission and digital diagnostics.
Question 3: In an industrial control network, what does the term 'determinism' refer to?
- The ability to encrypt all network traffic
- The guarantee that messages are delivered within a defined, predictable time frame (Correct answer)
- Automatic error correction in data packets
- Dynamic IP address assignment
Correct answer: The guarantee that messages are delivered within a defined, predictable time frame
Determinism in industrial networks means that message delivery times are bounded and predictable, which is critical for real-time control.
Question 4: Which OSI model layer is responsible for defining the electrical and physical characteristics of a fieldbus network cable?
- Application layer
- Transport layer
- Data link layer
- Physical layer (Correct answer)
Correct answer: Physical layer
The OSI Physical layer defines cable types, connectors, signal voltages, and bit-rate specifications for network media.
Question 5: What is the maximum number of devices that can be addressed on a single HART multidrop network segment?
- 4
- 15 (Correct answer)
- 32
- 64
Correct answer: 15
HART multidrop mode supports up to 15 devices on a single segment, with each device set to a unique polling address from 1–15.
Question 6: A control system technician needs to isolate a segment of an industrial Ethernet network for troubleshooting. Which device is used to create logical network segments at Layer 2?
- Router
- Hub
- Managed switch (Correct answer)
- Repeater
Correct answer: Managed switch
A managed switch operates at OSI Layer 2 and can create VLANs and manage traffic to logically isolate network segments.
CCST CCST Communications & Networking in Control Systems 1
Which industrial communication protocol uses a token-passing bus architecture and is commonly found in legacy process control systems?