Layer 1 expansion of a single LAN segment: Which physical layer (Layer 1) devices can be used to enlarge the area covered by a single Ethernet LAN segment?

Introduction / Context:
Ethernet collision domains in classic half-duplex environments can be extended at Layer 1 using devices that simply regenerate and repeat signals without interpreting frames. Understanding which components truly operate at Layer 1 helps avoid mixing in Layer 2 devices that change the broadcast/collision domain model.

Given Data / Assumptions:

• The listed devices are: 1) Switch, 2) NIC, 3) Hub, 4) Repeater, 5) RJ45 transceiver.
• The goal is to enlarge a single LAN segment, not to create separate segments.
• Focus is strictly on OSI Layer 1 behavior.

Concept / Approach:

Layer 1 devices forward bits without MAC learning or filtering. Repeaters (including multiport repeaters, i.e., hubs) extend signal reach and timing but keep a single collision domain. Switches are Layer 2 and segment collision domains; NICs and connectors/transceivers are endpoints/physical media, not segment enlargers by themselves.

Step-by-Step Solution:

Verification / Alternative check:

Topology drawings show a larger shared collision domain when hubs/repeaters connect multiple cables; switches would instead create multiple segments.

Why Other Options Are Wrong:

Switches (1) are Layer 2; they do not enlarge the same segment—they create new segments.

RJ45 transceivers (5) and NICs (2) are not used to extend a segment's geographic scope by repeating signals.

Common Pitfalls:

Assuming modern switches are Layer 1 because they have many ports; confusing media converters with repeaters; forgetting that hubs create a single collision domain that scales poorly.

Final Answer:

3 and 4