Cat 5 Wiring Explained: Standards, Diagrams & Step-by-Step Instructions

A wired network may seem old-fashioned in a Wi-Fi world, but it’s still the go-to choice when you need speed and stability. Cat 5 wiring has been the backbone of home and office Ethernet setups for years, providing a stable and fast link for everything from internet access and file sharing to streaming, gaming on a console or PC, and running IP security cameras.

The good news is, wiring Cat 5 cable yourself isn’t as complicated as it sounds. With a few tools and the right steps, you can create reliable connections, avoid common mistakes, and keep your network running smoothly. This guide will walk you through the essentials.

How Does Cat5 Wiring Work?

When people talk about Cat 5 cable wiring today, they usually mean Cat 5e (“enhanced”). Category 5 (Cat5) was the original standard, designed for 10/100 Mbps Ethernet at up to 100 MHz. These cables are obsolete and no longer manufactured for new installations.

Cat5e tightened performance specs to reduce electromagnetic interference and crosstalk and made 1 Gbps Ethernet possible over the same maximum channel length of 100 meters (328 ft).

Inside the Cat5 or Cat5e cable are four twisted pairs of copper conductors. The twisting cancels out electromagnetic noise so your data signal stays clean. For 10/100 Mbps networks, only two pairs are used for transmitting and receiving data. Gigabit Ethernet, on the other hand, uses all four pairs simultaneously to push higher speeds.

You’ll find two cable constructions in practice:

• Solid conductor: less flexible, but better for fixed in-wall runs or patch panels due to lower signal loss.
• Stranded conductor: more flexible, making it ideal for short patch cords that you move around.

Cat5 isn’t just for data — it can also deliver electrical power to devices through a standard called Power over Ethernet (PoE). This allows you to run a single cable that carries both network traffic and DC power to devices like 4K PoE security cameras, VoIP phones, or wireless access points. The result is a cleaner, simpler installation: fewer power adapters, fewer outlets, and more flexibility in where you place devices.

Cat5 Wiring Standards and Diagrams

Both Cat5 and Cat5e rely on the TIA/EIA-568 standards, which spell out how the eight individual copper wires inside the cable must be arranged. These wires terminate in an 8P8C modular plug — commonly called an RJ45 connector — the familiar clear plastic plug you snap into a network port.

The Two Standards: T568A and T568B

To ensure devices talk to each other correctly and data transmission stays consistent, two standardized Cat 5 wiring layouts are used: T568A and T568B.

• T568Bis by far the most common in the United States for both commercial and residential networks. If you’ve ever bought a pre-made patch cable, chances are it’s wired to B.
• T568Ais often specified in government and military installations. It also provides cleaner backward compatibility with older telephone systems, which is why some residential wiring standards still reference it.

They serve the same function, and performance is identical. The only difference is how the orange and green pairs are assigned.

Cat 5 Wiring Diagrams: How to Read the Pinouts

When you look at a diagram of Cat 5 wiring, orientation matters.

• View:Hold the plug with the latch down, gold pins facing you.
• Numbering:Pins are counted left to right, 1 to 8.
• Pairs:The cable contains four twisted pairs: Green, Orange, Blue, Brown (each with a white tracer mate).

T568A color order (pins 1→8):

1. white/green
2. green
3. white/orange
4. blue
5. white/blue
6. orange
7. white/brown
8. brown

T568B color order (pins 1→8):

1. white/orange
2. orange
3. white/green
4. blue
5. white/blue
6. green
7. white/brown
8. brown

The blue pair always occupies pins 4–5, and the brown pair always occupies pins 7–8. In T568A, the green pair sits on pins 1–2, while in T568B, it’s the orange pair.

Straight-Through vs. Crossover Cables

When you wire a Cat5/Cat5e cable, you’ll also need to choose between straight-through and crossover wiring, which comes down to how the pairs are arranged at each end.

Straight-through cables

Straight-through cables are what you’ll use almost every time. Both ends are terminated the same way—either T568A→T568A or T568B→T568B.

This makes sure the transmit pins on one device line up with the receive pins on the other. Use straight-through when connecting different types of devices: for example, a PC to a switch, or a switch to a router.

Crossover cables

Traditionally, crossover cables were used to connect two devices of the same type directly (like PC-to-PC or switch-to-switch) without a hub, router, or switch in between. The transmit (Tx) and receive (Rx) wire pairs had to be crossed so the devices could communicate.

At 10/100 Mbps, Ethernet only uses two pairs (pins 1–2 and 3–6). To create a crossover, you flip those pairs so transmit and receive cross:

• Pin 1 ↔ Pin 3
• Pin 2 ↔ Pin 6

That’s why a quick way to build a crossover is wiring one end as T568A and the other as T568B. The orange and green pairs are reversed, which achieves the swap.

For Gigabit Ethernet (1000 Mbps), all four pairs are active. A true crossover at this speed would also swap:

• Pin 4 ↔ Pin 7
• Pin 5 ↔ Pin 8

The reality today: Almost every piece of modern networking equipment supports Auto-MDI/MDI-X, which automatically detects whether a straight-through or crossover is needed and adjusts internally. That means you rarely need to build a crossover cable yourself, unless you’re keeping older hardware alive.

How to Wire Cat5 Cable

If you’re wiring today, you’re almost certainly using Cat5e even if people still say, “Cat 5.” The process is straightforward once you decide two things up front:

1. What you’re making:a patch cable (RJ45 plug on both ends) or a permanent link (in-wall run terminated to a keystone jack and/or patch panel).
2. Which pinout you’ll use:T568A or T568B. Performance is the same—just pick one and stay consistent across the whole install.

Also match the cable and hardware correctly: solid conductor cable for in-wall runs to jacks/patch panels; stranded cable for flexible patch cords to devices. Use plugs/jacks rated for the conductor type.

Tools & Materials You’ll Need

Cable and hardware:

• Cat5e bulk cable (choose solid copperfor permanent runs; avoid copper-clad aluminum)
• RJ45 (8P8C) modular plugs, or keystone jacks with wall plates
• Optional: pass-through RJ45 plugs and a matching crimper, strain-relief boots, patch panels

Tools:

• Cable jacket stripper or combo strip/crimp tool
• RJ45 crimp tool (standard or pass-through)
• Punch-down tool with a 110 blade (for jacks or panels)
• Flush cutters or electrician’s scissors
• Cable tester (at minimum a simple wire map tester; advanced certifiers if you need them)
• Labels and a fine marker, plus hook-and-loop ties (gentler than zip ties)
• Optional: fish tape, drywall saw, low-voltage mounting brackets for new wall plates

Best practice limits:

• Keep each channel ≤ 100 m (328 ft), usually 90 min-wall plus 10 m of patch cords
• Respect the bend radius(at least 4× the cable diameter) and don’t crush the jacket
• Maintain pair twists as close as possible to the termination, ideally ≤ 5 in (13 mm)of untwisted length

Step-by-Step Instructions: Wiring Your Cat 5 Cable

Making a Patch Cable (RJ45 plugs on both ends)

1. Measure and cut: Cut the cable to length, leaving a little extra for slack. If you’re using strain-relief boots, slide them on now.
2. Strip the jacket: Score about an inch (25 mm) of the outer jacket. Bend it to split the cut instead of sawing through — this avoids nicking the conductors.
3. Arrange the wires: Pick T568Aor T568B. Untwist only what you need and line the conductors up in the chosen order, with the plug’s latch facing down and pins facing you.
4. Straighten and trim: Comb the wires flat and trim them evenly. Leave about half an inch (12 mm) from the jacket to the tips if you’re using standard plugs. Pass-through plugs don’t require as precise a cut.
5. Insert into the plug: Slide the conductors all the way into the plug, keeping the order correct. Make sure the cable jacket sits under the plug’s strain tab.
6. Crimp: Crimp firmly once. Pass-through tools will also shear off the extra conductor ends.
7. Terminate the other end: For a normal patch cable, use the same standard on both ends (A→A or B→B). Only wire A→B if you intentionally need a 10/100 crossover for older equipment.
8. Test and label: Use a cable tester to check continuity and pinout. Label both ends so you know where the cable goes later.

Terminating an In-Wall Run to a Jack (and Patch Panel)

1. Plan the route and mount hardware: Install a wall box and wall plate where the cable will end. At the closet or rack, plan space for a patch panel or jacks.
2. Pull the cable: Feed solid Cat5e carefully, no sharp bends or tight pulls. Leave 6–12 inches of service loop at both ends. Support the cable loosely with Velcro ties.
3. Prep the cable: Strip 2–3 inches (5–7 cm) of jacket at the termination point. Keep the pairs twisted as long as possible.
4. Seat wires to the jack: Choose T568Aor T568B (match your standard). Most jacks have the color code printed right on them. Lay each pair into the IDC slots with the twist right up to the punch-down.
5. Punch down: Use the punch-down tool to seat and trim each wire in one press. Keep the jacket snug against the jack body. Snap the jack into the wall plate.
6. Terminate the other end: At the patch panel, follow the same color code. Use the panel’s cable management bar to secure the cable neatly.
7. Test the link: Use a tester to confirm continuity, length, and (if your tool allows) signal quality. Fix any miswires now.
8. Patch to equipment: Connect devices with short stranded patch cords, from the wall jack to a PC, or from the panel to a switch. Label everything clearly.

Putting Your Wiring to Good Use: PoE Cameras with NVR

If you’re wiring drops for security, a PoE NVR security systemkeeps things clean: one Cat5e cable per camera carrying both data and power, and your footage sits locally, no cloud fees or bandwidth surprises.

The eufy NVR S4 is a really solid hub for this. It comes ready for 24/7 local recording with 2TB of storage (expandable to 16TB), supports 8 camera channels out of the box (upgradable to 16), and handles PoE instantly, so you can just plug in the camera, and it works.

Here are two eufy PoE camera options that work perfectly with the S4 and make the most of your cabling work:

eufy PoE Bullet-PTZ Cam S4

This eufy PoE Bullet-PTZ Cam S4 gives you the best of both worlds: a 4K ultra-wide view to capture the big picture and a dual 2K+2K PTZ module (pan-tilt-zoom) that can auto-track and zoom in—up to 8×, with full 360° coverage. Together, that means you’ll get everything from sweeping scene context to sharp detail—like license plates or faces—up to about 164 feet away.

At night, it switches on Starlight color vision, giving you more natural-looking footage without needing a spotlight. You can still boost illumination using the built-in spotlight when needed, and HDR helps control glare from things like headlights.

On-device AI helps you ignore unimportant motion, focusing only on people, vehicles, pets, or strangers. Toss in two-way audio, flashing warning lights, and rugged IP65 weatherproofing, and you’ve got a camera that can handle just about any angle—especially with cross-camera AI tracking, which lets two units hand off motion between them if an object moves across your driveway or walkway.

eufy PoE Turret Security Camera E41

If you’d rather have a more compact option that still delivers sharp performance, the eufy PoE Turret Security Camera E41 is a great fit. It offers crystal-clear 4K resolution with a wide 122° field of view, plus a 5× digital zoom so you can crop in without losing detail.

What’s really handy is the adjustable tilt—once it’s mounted, you can tilt the head up to about 82° to fine-tune your view without re-mounting. That makes it perfect for tricky spots like eaves or tight corners.

Nighttime works just as elegantly: Starlight color for low-light viewing, spotlight for full-color shots, or infrared (IR) if you’d rather stay discreet. It comes with the same smart features as the PTZ: object detection AI, two-way audio, warning lights, plus a tougher IP67 rating, great for highly exposed outdoor areas. And of course, it’s powered via PoE, plugging straight into the S4 for seamless streaming and recording.

Conclusion

Setting up reliable wired connections doesn’t have to be complicated. By understanding how Cat 5 wiring works, following the right standards, and taking care during installation, you can build a network that handles everything from streaming and gaming to powering PoE security cameras. With the right tools and a bit of patience, your cables will deliver stable speed and clean power where you need it most.

FAQs

What does a Cat5 wire do?

A Cat5 cable is an older type of Ethernet cable that carries network data at up to 100 MHz and 10/100 Mbps over 100 meters. It was widely used in home and office networks before being replaced by Cat5e, which reduces interference and supports gigabit speeds. These cables connect devices like computers, routers, printers, and switches, and they can also deliver Power over Ethernet (PoE) to power IP cameras, wireless access points, VoIP phones, and smart devices through a single line.

What is the Cat5 wiring protocol?

Cat5 cables can be terminated using one of two wiring standards: T568A or T568B. Both work the same way, but it’s important to choose one and stick with it consistently throughout your installation. If one end of the cable is wired as T568A and the other as T568B, you end up with a crossover cable. These were sometimes required for older equipment, but most modern devices can automatically adjust, so either standard will work as long as it’s consistent.

What is the difference between Cat5 and Cat6?

The biggest difference between Cat5 (and Cat5e) and Cat6 cables is performance. Cat5 cables were designed for up to 100 MHz and speeds of 10/100 Mbps, while Cat5e improved on that to reliably support gigabit speeds. Cat6 steps things up with stricter standards and 250 MHz bandwidth, which means less interference and better performance. It can run 1 Gbps up to 100 meters and even reach 10 Gbps on shorter distances (about 55 meters). For that reason, Cat6 is preferred for modern networks, while Cat5 is now largely outdated.

Can I plug a Cat6 cable into a Cat5 jack?

Yes. Cat6 cables use the same 8P8C (RJ45-style) connectors as Cat5, so they’ll fit into Cat5 jacks without a problem. The connection will work, but the network speed will only be as fast as the lowest-rated part of the setup. In other words, if you connect Cat6 cable to a Cat5 jack, you’ll be limited to Cat5 performance. To get full Cat6 speeds, all components — cables, jacks, and patch panels — need to be rated Cat6 or higher.