1.5 Compare and contrast transmission media and transceivers
Connector Types
📘CompTIA Network+ (N10-009)
What is a BNC Connector?
A BNC connector is a type of coaxial cable connector used to attach coaxial cables to networking devices. It is designed with a bayonet-style locking mechanism that requires you to push the connector on and twist it to lock it in place. This gives a secure, stable connection that does not loosen easily.
BNC connectors were widely used in older data networks and are still used today in some specialized IT environments.
Key Characteristics of a BNC Connector
1. Used with Coaxial Cables
BNC connectors are mainly used with:
- RG-58 (Thinnet) coaxial cable
- 50-ohm impedance cables
- Sometimes 75-ohm versions for video applications
For the Network+ exam, remember:
✔ BNC = Coaxial cable → 50 ohms → Older Ethernet (10BASE2)
2. Bayonet Locking Mechanism
- Insert the connector
- Twist a quarter-turn
- Locks into place
This prevents accidental unplugging and keeps signals stable.
3. Supports Analog and Digital Signals
While it was used mainly in older Ethernet, BNC is still popular for:
- Radio frequency (RF) equipment
- CCTV security camera systems
- Test equipment (oscilloscopes, signal analyzers)
This is useful to know when the exam asks about where coaxial connectors are still used today.
Where BNC Was Used in Networking
1. 10BASE2 Ethernet (“Thinnet”)
Historically, BNC connectors were essential for early Ethernet networks that used a bus topology.
10BASE2 characteristics:
- Maximum distance: 185 meters per segment
- Speed: 10 Mbps
- Used T-connectors and terminators
Although 10BASE2 is not used in modern enterprise networks, it is important for the exam.
Exam Tip:
✔ BNC connectors were used in legacy Ethernet networks → 10BASE2
✔ They are no longer common in modern LANs but may be seen in older industrial systems.
Common BNC Components You Should Know
1. BNC Connector
The standard plug on the cable end.
2. BNC T-Connector
Used in 10BASE2 to connect:
- A computer network interface card (NIC)
- The coax segment running in both directions
This allowed all devices to share one cable segment.
3. BNC Terminators
Placed at both ends of a 10BASE2 network segment:
- Value: 50 ohms
- Purpose: Stop signal reflections and maintain signal quality
Exam Tip:
If the exam mentions “signal reflection on coaxial cable networks,” the answer typically involves missing or faulty terminators.
Impedance: 50-ohm vs. 75-ohm BNC
The exam may ask about the difference:
50-ohm
- Used for data networking
- Used with RG-58
- Used in RF signal equipment
75-ohm
- Used for video signals (CCTV, broadcast systems)
For CompTIA Network+, focus on:
✔ 50-ohm = used in networking
✔ 75-ohm = used mostly for video
Advantages of BNC Connectors
- Strong, secure locking design
- Low signal loss (good for RF and coaxial systems)
- Durable and resistant to physical strain
- Good for high-frequency signals
Disadvantages (Important for the Exam)
- Not used in modern Ethernet networks
- Shared coaxial designs (like 10BASE2) were less reliable
- Harder to scale
- Any cable break can bring down the entire segment
These limitations are reasons why twisted pair (RJ45) and fiber optic connectors replaced BNC in networking.
Where You Might Still See BNC in IT Environments
These are valid IT-based real examples without unrelated comparisons:
- Security camera systems (CCTV)
- Broadcast and media production equipment
- Radio and wireless testing equipment
- Laboratory instruments such as oscilloscopes
- Legacy industrial networks still running on coaxial connections
What You Need to Remember for the CompTIA Network+ Exam
Here is a summary of the most important exam-relevant points:
✔ BNC is a connector type used with coaxial cable
✔ Uses a bayonet twist-lock mechanism
✔ Commonly associated with 10BASE2 Ethernet (Thinnet)
✔ Requires T-connectors and 50-ohm terminators
✔ Older technology—rarely used in modern LANs
✔ Still used in CCTV, radio equipment, and test devices
✔ Comes in 50-ohm and 75-ohm versions
If you remember these points, you can answer nearly any Network+ question about BNC connectors.
