Arquivo de IT (Information Technology) - Electronic Circuits

UTP vs STP vs FTP: Anatomy of Shielded Network Cables

Electronic Circuits — Wed, 18 Mar 2026 07:51:32 +0000

UTP vs STP vs FTP: Anatomy of Shielded Network Cables

🌐 You can read this article in: Português | Español

If you have ever faced mysterious connection drops or slowness in environments with many electrical cables, you know that a network cable is much more than just copper and plastic. Many installers and enthusiasts make the mistake of ignoring the physics behind data transmission, treating any 'blue cable' as equal.

Today, we will dissect the engineering behind the acronyms UTP, STP, and FTP, including the variations U, F, S, and SF. More than memorizing letters, you will understand how to protect your infrastructure against 'electromagnetic chaos' and ensure that the contracted speed is, in fact, the delivered speed.

1️⃣ The Theory Behind: Differential, Electromagnetism, and Grounding

To understand why network cables use different levels of protection and shielding, it is important to start with the physical basis of Ethernet operation. In modern networks (especially Gigabit Ethernet and above), transmission occurs via differential signals in twisted pairs.

In this method, the transmitter sends the same signal through two conductors, but with opposite polarities, usually represented as V+ and V−. The receiver does not measure each wire individually; instead, it interprets the voltage difference between the two conductors, known as the differential voltage:

Vdiff = (V+) - (V-)

This type of transmission offers great resistance to external interference. When an external electromagnetic field hits the cable, it tends to induce a voltage practically equal in both conductors. This phenomenon is called common-mode noise (common-mode noise). Since the receiver calculates only the difference between the signals, this noise is largely canceled.

The twisting of the pairs further reinforces this effect. By constantly alternating the physical position of the conductors along the cable, exposure to the external electromagnetic field is distributed evenly, improving the natural cancellation of interference.

However, in environments with high electromagnetic density, such as industrial installations, data centers, or locations with a strong presence of radio frequency (RFI), this passive cancellation may not be sufficient. In these scenarios, problems such as crosstalk (crosstalk) also arise, where the signal from one wire pair induces interference in an adjacent pair due to capacitive and inductive coupling between them.

This is the point where cable shielding becomes relevant. Metallic layers such as meshes or conductive foils function similarly to a Faraday cage, reducing the penetration of external electromagnetic fields and limiting coupling between internal pairs. When properly grounded, the shielding can also help drain common-mode currents, contributing to signal stability.

Another fundamental aspect in the performance of Ethernet cables is Characteristic Impedance (Z₀). For twisted pair cables used in Ethernet networks, the standard specified by structured cabling standards is:

Z₀ = 100 Ω ± 15%

In practice, this means that the cable impedance must remain approximately within the range of 85Ω to 115Ω throughout the entire link.

This impedance depends directly on the distributed electrical properties of the transmission line, mainly inductance (L) and capacitance (C) per unit length. In an ideal approximation, the relationship between these parameters is expressed by:

Z0 = √(L / C)

Any physical change in the cable can modify these parameters. Crushing, excessive bending, twisting, or deformations of the pair geometry alter the distance between conductors and the electromagnetic field around them. This changes the local impedance of the cable and can cause impedance discontinuities.

When this occurs, part of the signal energy does not move forward through the cable and is reflected back towards the transmitter. These reflections degrade signal integrity and can reduce the effective data rate, especially in high-speed networks such as Gigabit Ethernet and 10 Gigabit Ethernet.

For this reason, both the geometric design of the cable and the correct application of shielding and grounding are critical factors to ensure electromagnetic integrity and network communication performance.

2️⃣ The "Core": Deciphering the Acronyms in Practice

Now that we understand the physics, we need to standardize the vocabulary. Manufacturers use international acronyms that make up the cables, usually in the format "U/UTP". The first letter refers to the overall cable shield, and after the slash "/", it refers to the shielding of the internal pairs. Let's dissect each one visually.

Nomenclature Components

Before entering the full models, let's understand the basic letters:

U - Unshielded (No Shielding)
F - Foil Shielding (Aluminum Foil Shielding)
S - Braided Shielding (Metal Mesh Shielding)
SF - Braided + Foil Shielding (Double Shielding: Mesh and Foil)

U/UTP - Unshielded / Unshielded Twisted Pair

U - Unshielded
UTP - Unshielded Twisted Pair
The most common standard, with no shielding surrounding the cable or the pairs.

Fig. 2 – U/UTP Ethernet Cable: No additional protection.

F/UTP - Foiled / Unshielded Twisted Pair

F - Shielded with Aluminum Foil
UTP - Unshielded Twisted Pair
Has an aluminized foil surrounding the entire cable, but the internal pairs do not have individual shielding.

Fig. 3 – F/UTP: Note the aluminum foil surrounding all pairs.

S/UTP - Braided Shielding / Unshielded Twisted Pair

S - Shielded with Braid or Mesh
UTP - Unshielded Twisted Pair
Uses a metallic mesh (screen) to protect the entire cable, ideal against mechanical and low-frequency interference.

Fig. 4 – S/UTP: Robust protection via external braided mesh.

SF/UTP - Braided Shielding + Foil / Unshielded Twisted Pairs

SF - Shielded with Mesh + Shielded with Aluminum Foil
UTP - Unshielded Twisted Pair
The combination of both shields (Mesh + Foil) surrounding the cable offers maximum external protection.

Fig. 5 – SF/UTP: The definitive shielding against external interference.

S/FTP - Braided Shielding / Foiled Twisted Pair

S - Shielded with Mesh (Global)
FTP - Shielded Twisted Pair (Individual)
Here each pair is individually shielded (foil) and there is an external mesh. The ideal standard for heavy industry and data centers.

Fig. 6 – S/FTP: Detail of individual shielding on each pair (foil) and global mesh.

F/FTP - Foiled / Foiled Twisted Pair

F - Shielded with Aluminum Foil (Global)
FTP - Shielded Twisted Pair (Individual)
Foil shielding surrounding the entire cable and foil on each pair. Common in Cat 6a cables to prevent Alien Crosstalk.

Fig. 7 – F/FTP: Double layer of aluminum foil.

U/FTP - Unshielded / Foiled Twisted Pairs

U - Unshielded (Global)
FTP - Shielded Twisted Pair (Individual)
There is no general protection on the cable, but each pair has its own foil shielding. Great for reducing internal crosstalk without the cost of global shielding.

Fig. 8 – U/FTP: Individually shielded pairs, no general protection.

3️⃣ Best Practices and Installation "Pro Tips"

Buying an expensive shielded cable does not guarantee performance. Installation is the weakest link. Here is what separates the amateur installer from the engineer:

1. Grounding is Mandatory (and critical): A shielded cable (FTP, STP, S/FTP) does not function as an antenna (which absorbs noise). If you do not ground the shielding correctly at both ends (at the patch panel and the RJ45 connector), it can act as an antenna, picking up noise and injecting it into the signal via capacitance. Use metallic connectors and patch panels and ensure that the drain wire makes continuous contact with the connector housing.

2. Bend Radius: Do not crush the cable. When bending excessively, you alter the twist pitch of the internal pairs and the distance between conductors, destroying the impedance balance. The rule of thumb is not to bend the cable in a radius smaller than 4 times the outer diameter of the cable for horizontal cables.

3. Stripping: When preparing the cable for crimping, do not remove more than 25mm of the outer jacket. If you strip too much and expose the twisted pairs without the protection of the shielding (in FTP/STP cables), you create a signal leakage point. The shielding needs to cover the signal as close as possible to the connector pin contact.

4. Beware of the Skin Effect: At high frequencies (Gigabit Ethernet), current tends to flow over the outer surface of the conductor. Therefore, braided shields (braid) are generally more effective than flat foils alone, as they offer more surface area to drain low-frequency interference.

🤔 Frequently Asked Questions (FAQ)

We clarify the main technical doubts about choosing and installing shielded network cables.

What is the real difference between STP and FTP? 🔽

RJ45 Ethernet Cable Color Standard – T568A and T568B – EIA/TIA Standard

Electronic Circuits — Sat, 31 Dec 2022 16:14:00 +0000

Demystifying RJ45 Ethernet Cable Color Standards: T568A vs. T568B in EIA/TIA Standard

🌐 You can read this article in: Português | Español

Back in the past, a few decades ago, there were no standard regulations for the wiring of structured networks in the IT industry.

The standards for these networks were decided upon by the companies or professionals responsible for installing the wired networks.

This lack of standardization made it difficult to maintain or modify the network structures of companies, especially when done by another company or professional.

To address this issue and with the increasing growth of technology and infrastructure for wired networks, the TIA/EIA standards were developed.

In 1991, the TIA/EIA, 568A and 568B standards were introduced by the Electronic Industries Association (EIA) and the Telecommunications Industry Association (TIA) to standardize the electrical and electronic connections of network cables and their connections.

The 568A standard was revised in 1994 to include Category 4 and Category 5 (UTP – Unshielded Twisted Pair) wiring, and in 2001 the EIA/TIA 568-B standard was published, covering a total of 10 different categories.

📖 T568A and T568B Categories

There are two different categories of TIA/EIA standards, commonly known as RJ45 Standard B and RJ45 Standard A, which are actually T568A and T568B.

These are termination standards used by Internet Providers, Backbone Infrastructure, Industrial Wiring Infrastructure, and also by small businesses and residential wiring.

However, the difference between these two categories is that the orange/white and green/white pairs, which correspond to pins 1 & 2, 3 & 6, are exchanged in the assembly of the cable, as illustrated in Figure 2 below.

Fig.2-Standard-Colors-Cable-Network-RJ45-T-568A-T-568B-Standard-EIA/TIA

It is worth remembering that even with changes to the set of pairs, when the same standards are used at both ends of the cable, the results will be the same, with direct connections at their ends.

In Table 1 below, we have the configuration of the pins and their corresponding colors, following the two standards side by side for comparison.

📌 Sequential Table of Colors and Pinning Standard T-568A and T-568B

Pin	T-568A	T-568B
1	White/Green	White/Orange
2	Green	Orange
3	White/Orange	White/Green
4	Blue	Blue
5	White/Blue	White/Blue
6	Orange	Green
7	White/Brown	White/Brown
8	Brown	Brown

The T568A standard is the widely accepted standard because it is compatible with most wiring schemes and is what I recommend for most applications.

ℹ️ Crossover Cable

Crossover cables, use the T-568A and T-568B standards at each end as illustrated in Figure 3 below. These categories of cables are used when we need to, for example, connect two computers or laptops without using a router or switch.

Fig. 3 – Connection of Crossover Cable Standards T-568A and T-568B

It is worth remembering that if you are still using older equipment, you should not connect crossover cables between the computer and a switch or router, as in some cases it can damage the equipment.

Now if you work with newer, more modern equipment, they use AUTO MDI/MDIX technology, which automatically identifies the connected interface and even if it is of the crossover type, there is no problem, as it automatically configures itself.

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,
The ElCircuits Team ⚡

O post RJ45 Ethernet Cable Color Standard – T568A and T568B – EIA/TIA Standard apareceu primeiro em Electronic Circuits.

How ATX Power Supplies Work – Diagnose Problems in 10 Easy Steps

Eng. Jemerson — Mon, 14 Sep 2020 23:33:00 +0000

How ATX Power Supplies Work: Learn to Diagnose Problems in 10 Simple Steps

Hello, electronics enthusiasts!

🌐 You can read this article in: Português | Español

ATX Switched-Mode Power Supplies have some interesting features when compared to standard Switched Mode Power Supply (SMPS).

In the ATX power supply, there are different output voltages: + 12V, + 5V, + 3.3V, -12V, -5V and 5VSB. There are some variations on these types of Power Supply, but in the general context, the pattern is this.

The way SMPS work is pretty much the same.

They control the output voltage by opening and closing the switching circuit so as to maintain the opening and closing time of this circuit, that is, the width of pulses and their frequencies, to obtain the desired voltage.

There are separate processes for everything to work smoothly. So let’s see the modular diagram to unravel the steps of these processes so that we can step by step understanding.

This is the block in modules divided by steps, to improve our understanding.

There are distinct processes that need to work together for everything to function properly. Let’s take a look at the modular diagram to break down each step and better understand how these processes unfold.

There are 10 basic steps involved in operating an ATX power supply, although there are additional underlying modules that are intrinsically connected to these steps.

We won’t go into too much depth here, but for those who want a more detailed explanation, we’ve included a video in Portuguese at the end of this article, created by our partner site.

So let’s understand these steps:

Step 1 – Transient Filter

Is through that stage that the voltage coming from your network, whether 110 or 220V AC should enter.

Fig. 2 – How SMPS Works – Transient Filter

This voltage goes through basic protection, fuse, that if some step ahead short, the fuse opens, avoiding to burst everything ahead, and in the same line, we have NTC (Negative Temperature Coefficient), It’s a surge current limiter, in series with the electric circuit.

In its value of ohmic resistance decreases as its temperature rises, its initial resistance is approximately 15 Ohms, which we can understand by the Ohms’ law, advantages one has in using it in series after the power supply switches it on lowers its resistance to approximately 0.5 Ohms.

EMI filters also exist, these are used to avoid high-frequency noise and a huge amount of harmonics generated by the switches that can propagate through the electrical network and cause interference in nearby electronic equipment.

Step 2 – Primary Rectification

Fig. 3 – How SMPS Works – Primary Rectification

In this stage we find the rectifier bridge or an arrangement formed by four common diodes, which has the function of rectifying a full-wave voltage, that is, rectifying an alternating electric current (AC), transforming it into a continuous electric current (DC).

Step 3 – Filtration

Fig. 4 – How SMPS Works – Filtration

After rectification, the DC signal, Ripples (which are small variations, capacitors are responsible for filtering and stabilization IE, a decrease of these Ripples, in the rectified voltage, this voltage rises to something around 300V, which are used in power switches, this part is fundamental to the correct stabilization of source especially if its source is of high power.

Step 4 – Power Switches

Fig. 5 – How SMPS Works – Power Switches

These switches can be Bipolar Power Transistors such as MOSFETs, or any other type, but they differ from ordinary transistors, by the type of operation in which these transistors work.

These switching transistors dissipate less power than a common working transistor in a linear source because they work as a switch on/off at high speeds, depending on the design of the source, they suffer variations that are usually between 20Khz to 100kHz.

They are directly responsible for the output voltage, and stability of that voltage, through of the commands received by the Control Circuit.

Step 5 – Output Transformer

Fig. 6 – How SMPS Works – Output Transformer

The transformer is a high-frequency CHOPPER TRANSFORMER, and they also work with alternating voltage, when passing through the switches voltage will be a square wave AC type PWM, but with high frequency, not with the same frequency of 60Hz of the input voltage.

The switches work on two different levels, High and Low, when it is HIGH, voltage goes through it normally, causing a constant voltage level in the input of coil of the transformer, action of these transistors, goes from HIGH to LOW very quickly.

This will induce the winding to have the necessary voltages according to the winding and frequency placed on these switches.

Step 6 – Fast Rectifier

Fig. 7 – How SMPS Works – Fast Rectifier

With the voltage generated by high-frequency switches, a diode is needed to meet this demand, so we have the high-speed diodes called SCHOTTKY DIODES or fast recovery diodes since ordinary diodes would not be able to work with high-frequency voltages.

Step 7 – Output Filters

Fig. 8 – How SMPS Works – Output Filters

The inductor – This has the function of eliminating high-frequency harmonics so that they do not travel to the equipment that will be fed, imagine if these harmonics pass to a micro-controller for example, could cause undue loads and errors of reading in the control processes.

And the Capacitors – They are the ones that filter and stabilize the voltage at the output, avoiding ripples and instabilities at the output.

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If you liked this project, you might also be interested in these other articles:

Step 8 – Driver Transformer

Fig. 9 – How SMPS Works – Driver Transformer

The driver transformer in this case is nothing less than one responsible for traffic of information coming from the Integrated Circuit Controller, and pass these commands to the switches, so as to bring insulation or electrical decoupling between primary and secondary.

In this topology there is a pair of transistors that also switch the Transformer Drive to receive these PWM pulses from the driver IC, passing this information to the power step we already saw in Step 4.

Step 9 – PWM control

Fig. 10 – How SMPS Works – PWM control

The brain of a switched source is its PWM controller, they are dedicated integrated circuits, to perform that work, but they do not work alone, there are also current sensors, which also vary from source to source, but it is very likely that you will find in its source TL341 IC, it has the aspect of a transistor, but, it is not a transistor, it is very popular for its cost-benefit.

This circuit is connected to the output of the power supply, receives Feedback, and directs the voltage information to the IC that controls the oscillator that generates a rectangular signal whose pulse width is controlled and sent to the Transformer Drive that sends these commands to the step of power.

If the power at the output to raise the voltage tends to drop, the circuit activates the instantaneous correction in the pulse width of the switching transistors and the voltage keeps stabilized.

Step 10 – Primary Power Supply VSB

Fig. 11 – How SMPS Works – Primary Power Supply VSB

VSB stands for Voltage Standby, which is technically a power supply that keeps its output active, whenever the source power cord is connected to the mains, its capacity is approximately 2 Amps, and this depends on the total power of the source.

This active voltage line is to keep the circuit active and is necessary for when the power on button is activated through PSON, which is the start of the power supply, then the oscillator will activate the power line also powers the motherboard hardware to activate peripherals via software, keyboard, network, and so on.

For those who want a more in-depth, step-by-step explanation, we recommend watching the detailed video (in Portuguese) available on our partner’s YouTube channel. It complements this article with visual support and additional insights.

[Watch the original video in Portuguese in video below or – Click Here

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,
The ElCircuits Team ⚡

O post How ATX Power Supplies Work – Diagnose Problems in 10 Easy Steps apareceu primeiro em Electronic Circuits.

Arquivo de IT (Information Technology) - Electronic Circuits

UTP vs STP vs FTP: Anatomy of Shielded Network Cables

1️⃣ The Theory Behind: Differential, Electromagnetism, and Grounding

2️⃣ The "Core": Deciphering the Acronyms in Practice

Nomenclature Components

U/UTP - Unshielded / Unshielded Twisted Pair

F/UTP - Foiled / Unshielded Twisted Pair

S/UTP - Braided Shielding / Unshielded Twisted Pair

SF/UTP - Braided Shielding + Foil / Unshielded Twisted Pairs

S/FTP - Braided Shielding / Foiled Twisted Pair

F/FTP - Foiled / Foiled Twisted Pair

U/FTP - Unshielded / Foiled Twisted Pairs

3️⃣ Best Practices and Installation "Pro Tips"

🤔 Frequently Asked Questions (FAQ)

RJ45 Ethernet Cable Color Standard – T568A and T568B – EIA/TIA Standard

Demystifying RJ45 Ethernet Cable Color Standards: T568A vs. T568B in EIA/TIA Standard

📖 T568A and T568B Categories

You may be interested in:

📌 Sequential Table of Colors and Pinning Standard T-568A and T-568B

ℹ️ Crossover Cable

How ATX Power Supplies Work – Diagnose Problems in 10 Easy Steps

The way SMPS work is pretty much the same.

So let’s understand these steps:

Step 1 – Transient Filter

Step 2 – Primary Rectification

Step 3 – Filtration

Step 4 – Power Switches

Step 5 – Output Transformer

Step 6 – Fast Rectifier

Step 7 – Output Filters

🔗 Related Content

Step 8 – Driver Transformer

Step 9 – PWM control

Step 10 – Primary Power Supply VSB