# ATX > [!note]- Notes on power supply connectors > ![[Power Supply Connectors And Pinouts by MODDIY]] ## 15-pin connector ... ## 20-pin connector ... ## 24-pin connector ... ## 48-pin connector ... # Containerization ... # Crosstalk Crosstalk, in the context of cables with twisted pairs, is the level of interference measured in one twisted pair which is caused by the electromagnetic field generated by another twisted pair as a signal travels through it. Shielding the twisted pairs in a copper cable helps to mitigate this interference. > [!note]- Notes on crosstalk in copper network cables > ![[What Is Crosstalk In Copper Network Cables by Patch Cords Online]] # EMI EMI is an acronym which stands for "ElectroMagnetic Interference." This is the type of interference that causes crosstalk. # Host machine ... # Hub A hub is a node which broadcasts data from one connected device to all other connected devices indiscriminately. > [!note]- Notes on network hubs > ![[Network Hub by Jessica Scarpati]] # Hypervisor ... # IEEE IEEE stands for the Institute of Electrical and Electronics Engineers. > [!example] Example of the IEEE standard naming convention > IEEE 802.1D-2004 > * 802 - The committee. 802 is the LAN / MAN Standards Committee (LMSC). > * 1 - The working group. 802.1 is the Higher Layer LAN Protocols Working Group. > * D - The amendment or revision of the standard. This revision defined Media Access Control (MAC) Bridges for LANs and MANs. > * 2004 - The year that the revision was published. This revision was published in 2004. # IEEE 802 [(1)](https://www.ieee802.org/) IEEE 802 is the LAN / MAN Standards Committee (LMSC). They develop standards for LANs, MANs, and other area networks. # IEEE 802.1 IEEE 802.1 is the Higher Layer LAN Protocols Working Group of the LMSC. They develop standards for: * LAN / MAN architecture. * Inter-networking between other 802 LANs, MANs, and WANs. * LAN Security. * Overall LAN management. * Protocol layers above the MAC and LLC layers. # IEEE 802.1D > [!quote] Title of IEEE 802.3AT > IEEE Standard for Local and metropolitan area networks: Media Access Control (MAC) Bridges IEEE 802.1D is a standard originally published by the IEEE in 1990. In 2014, it was superseded by IEEE 802.1Q and IEEE 802.1AC. It's not yet officially withdrawn, but it will be eventually. # IEEE 802.1X > [!quote] Title of IEEE 802.1A > IEEE Standard for Local and Metropolitan Area Networks--Port-Based Network Access Control # IEEE 802.3 [(1)](https://www.ieee802.org/) IEEE 802.3 is the Ethernet Working Group of the LAN / MAN Standards Committee (LMSC). They develop standards for Ethernet networks. # IEEE 802.3AB > [!quote] Title of IEEE 802.3AB > IEEE Standard for Information Technology - Telecommunications and information exchange between systems - Local and Metropolitan Area Networks - Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications - Physical Layer Parameters and Specifications for 1000 Mb/s Operation over 4-Pair of Category 5 Balanced Copper Cabling, Type 1000BASE-T IEEE 802.3AB defines a variant of Gigabit Ethernet (transmitting Ethernet frames at a rate of a gigabit per second) over UTP Cat 5, Cat 5e, or Cat 6 copper cables called 1000BASE-T. That term is synonymous with the name of this standard. # IEEE 802.3AF IEEE 802.3AF is the original standard that describes how to deliver power over Ethernet cables. When you use the term "PoE," you're referring to this standard. # IEEE 802.3AT > [!quote] Title of IEEE 802.3AT > IEEE Standard for Information technology-- Local and metropolitan area networks-- Specific requirements-- Part 3: CSMA/CD Access Method and Physical Layer Specifications Amendment 3: Data Terminal Equipment (DTE) Power via the Media Dependent Interface (MDI) Enhancements # Injector ... # Inverter ... # Jitter Jitter is any deviation in the signal pulses of a high-frequency digital signal. > [!note]- Notes on jitter > ![[Jitter by Linda Rosencrance and John Burke]] # LCD Liquid Crystal Displays (LCDs) are a type of display which uses liquid crystal molecules to control light. These liquid crystal molecules are placed between two glass substrates, two polarizing filters, and are controlled with two transparent electrodes, one of which is connected to a Thin Film Transistor (TFT). Using a backlight, light shines through these layers and is filtered in such a way that it creates images depending on whether or not the liquid crystal molecules allow it to pass through certain sub-pixels. Voltage is used to control the orientation of the liquid crystal molecules. Depending on the type of LCD, the liquid crystal molecules will be oriented in a certain way without a voltage being applied. When a voltage is applied, the liquid crystal molecules will align themselves with the electric field that's generated from it. The alignment of these liquid crystal molecules determines whether or not light can pass through from the backlight to the outside world. ## Polarizing filter Imagine a picket fence with a rope going through the middle of two slats. If you move the rope up and down on one side, the rope would move accordingly on the other side. However, if you tried to move the rope at any other angle, like left to right or diagonally, the rope wouldn't move on the other side. A polarizing filter is like a picket fence, but with light waves. It's important to note, however, that it doesn't use physical slits or gaps like a picket fence. Unpolarized light is like the rope moving in all directions. A polarizing filter only allows light whose waves are moving up and down (or oscillating) in a certain direction to pass through. That "certain direction" in which light is oscillating is called its polarization. Specifically, its linear polarization. In our picket fence example, the fence only allowed vertical polarization due to the gap formed by the slats. This is called the polarization axis, or the direction which the polarization has to match in order for it to pass through the filter. Polarized light is like the movement of the rope on the other side of the fence from where the rope was being moved. It's light that has been filtered so that it has specific linear polarization. The polarizing filters in an LCD are arranged so that they lay on top of one another (sandwiching some of the other layers) and have their polarization axes perpendicular to each other (like city streets that form square city blocks). If you were to shine a light on either side of the polarization filters, no light would pass through. This is because the polarization filters block each other's polarization axes. Why would LCDs have this arrangement, then, if their purpose is to emit light? That's where the liquid crystal molecules and the transparent electrodes come in. ## Liquid crystal For light to pass through those polarizing filters, you would need to somehow change the polarization of the light as passes between them. Is this possible? It is with substances known as liquid crystals (LCs)! A liquid crystal molecule is like the needle of a compass. A compass needle is a tiny magnet that aligns itself with a magnetic field, typically the Earth's. A liquid crystal molecule is a tiny, rod-like molecule with a permanent electric dipole that aligns itself with an electric field. Liquid crystal molecules have a unique property which allows them to change the polarization of light through a phenomenon known as birefringence. They have this property because of their shape and how light travels through translucent material. The liquid crystal molecules themselves are inherently anisotropic. If a material made up of them has a large amount of the molecules aligned in the same direction, it's also anisotropic. But, if the average alignment of the molecules is pretty small, the material as a whole is isotropic. > [!example]- Example of the difference between isotropic and anisotropic > Isotropic is a term which refers to something having a physical property which stays the same no matter what direction you measure it. > > Anisostropic is a term which means the exact opposite. It refers to something having a physical property that changes depending on how you measure it in different directions. > > If you play video games, you may be familiar with texture filtering settings like bilinear / trilinear and anisotropic filtering. What is the difference between them? > > Regular texture filtering, like bilinear or trilinear, is applied isotropically. This means that it is applied in the same way regardless of how the camera is positioned relative to it. The surfaces immediately surrounding you will look fine. But, as they extend outwards and form sharper angles with the camera, they start getting blurrier and blurrier. > > Anisotropic filtering is different in that it applies filtering with the position of the camera relative to the surface in mind. It finds which direction is being compressed and which is being stretched from your perspective. The compressed dimension is going to have more texture detail within a given amount of screen space (pixels). The stretched dimension is going to have less texture detail within a given amount of screen space (pixels). To compensate for this inbalance, more samples are taken along the stretched dimension and the compressed dimension is either sampled normally or less. > > This way, textures look clear regardless of what angle they are being viewed from. In terms of visual clarity, anisotropic filtering looks better compared to bilinear / trilinear filtering. > >  How the liquid crystal molecules are oriented and when is what differentiates the three different types of LCDs. ## TN Twisted Nematic (TN) LCDs are based on the twisted nematic field effect. Without a voltage applied, the liquid crystal molecules orient themselves like a helical staircase from the front to the back. Crucially, the liquid crystal molecules on either side line up with the polarization axis of their respective polarizing filters. This default alignment is created by sandwiching two additional layers, one on either side of the liquid crystal molecules, which are rubbed to create microscopic grooves. The direction of these grooves match the polarization axis of the polarizing filter they are next to, and it causes the liquid crystal molecules near those grooves to line up with them. When light passes through the liquid crystal molecules in their helical shape, the polarization of the light changes as it moves through. The polarized light goes from having vertical polarization (after it passes through the first polarization filter), to horizontal polarization (after it moves through the liquid crystal molecules just before the second polarization filter). Since the polarization of the light now matches the polarization axis of the second polarization filter, it can shine through.  In a TN display, the two electrodes on either side of the liquid crystal molecules. When a voltage is applied, an electric field is created which runs perpendicular to the glass substrates. The helical shape of the liquid crystal molecules is disrupted and prevents the light's polarization from changing to match the polarization axis of the second polarization filter. As a result, the light isn't able to shine through and the sub-pixel appears black.  ## IPS In-Plane Switching (IPS) LCDs work on the same principles mentioned before, but differ in two aspects: 1. The two electrodes are on the same piece of glass (glass substrate) instead of on opposite sides of the liquid crystal molecules. 2. The liquid crystal molecules are always parallel with the glass substrates. They rotate on one plane, or in-plane. When voltage isn't applied, the liquid crystal molecules orient themselves at an angle perpendicular from the polarization axis of the second polarizing filter. This causes the light from the backlight to not come through. When a voltage is applied, an electrical field is created which runs parallel to the glass substrates. The liquid crystal molecules line up horizontally with the electric field.  ## VA A Vertical Alignment (VA) LCD also works on the same principles as the other LCD types. Without a voltage applied, the liquid crystal molecules orient themselves vertically, or perpendicular to the glass substrates. When light passes through the liquid crystal molecules in this orientation, the polarization of the light doesn't change as it moves through. Since the polarization of the light doesn't change to match the second polarization filter, it doesn't shine through. With a voltage applied, an electrical field is created that runs perpendicular to the glass substrates like in a TN LCD. The liquid crystal molecules orient themselves closer to being horizontal like in an IPS LCD. When light passes through the liquid crystal molecules inn this orientation, the plane of polarization of the light rotates by 90 degrees. Since the polarization of the light now matches the polarization axis of the second polarization filter, it can shine through. # Load balancer A load balancer is a node which distributes network traffic across a server farm. > [!note]- Notes on load balancers > ![[Load Balancing by Kinza Yasar and Alissa Irei]] # Media converter ... # Metro-Ethernet Metro-Ethernet is a Metropolitan Area Network (MAN) based on Ethernet standards. # PoE PoE stands for Power over Ethernet. # PSTN PSTN stands for "Public Switched Telephone Network." # RAID ... # Router > [!note]- Notes on network routers > ![[04. How Routers Work]] # Sandboxing ... # Sideloading ... # Signal attenuation Signal attenuation is the gradual reduction of the strength of a signal. For cables, signal attenuation is affected by the material and length of the cable. # STP STP stands for Shielded Twisted-Pair. > [!note]- Notes on Shielded Twisted Pair (STP) > ![[What Is Shielded Twisted Pair (STP) And How Does It Work by Gavin Wright]] # Stress testing ... # SuperSpeed USB ... # Tap ... # Virtual machine ... # Virtual switch ...