![]() ![]() The internal hardware architecture of the L1 switch allows the L1 switch to duplicate any incoming data to any number of output ports at full wire speed without dropping a single bit. L1 switches have very low latency and do not store or manipulate a single bit in the data stream. Once a connection is made between two ports the attached devices are essentially directly connected. L1 switches on the other hand, are fully transparent to the traffic going through them. Also the differing clock timing forces the PHY on the L2 switch to add/delete idle characters to compensate, making it impossible to compare input data streams to output data streams when testing using an L2 switch. In L2 switches, the output bit stream is different from the input bit stream in that MAC control frames, such as pause frames, are discarded by the MAC layer. Using Layer 2 (L2) switches for connection purposes in a test environment can cause a number of problems. In testing environments, this allows the tests to be as accurate as if there were a patch cord between the devices. Completely transparent connections between ports is performed based on software commands sent to the L1 switch over its control interface. They existed in the first fraction of a second of the universe, but disintegrated very quickly to become particles in the first family.The easiest way to think of a Layer 1 (L1) switch, also known as a physical layer switch, is as an electronic patch panel. (The particles of the second and third families are not part of ordinary matter. The first family, which includes the electron, the electron neutrino and the up and down quarks, gives us the familiar matter in the form of protons, neutrons and electrons. The discovery that neutrinos have a very small mass, at least a million times lighter than the electron, raises the possibility that neutrinos get their mass from unknown processes, that may not be related to the recently discovered Higgs boson.Īll fundamental matter particles are for some mysterious reason organised into three distinct families. Most neutrinos pass right through the Earth without ever interacting with any single atom.īecause neutrinos were produced in great abundance in the early universe and rarely interact with matter, there are a lot of them in the universe. Since neutrinos do not interact electrically or strongly, they almost never interact with any other particle. The sun produces millions of neutrinos in the internal fusion reactions that power it. Neutrinos are produced in a variety of interactions. The tauon has a very short lifetime – 100,000 times shorter than that of the muon. It is the most massive of the leptons, having a mass about 3,490 times the mass of the electron and 17 times that of the muon. The tauon was discovered in high-energy particle collision experiments between 19 by Martin Perl with his colleagues at Stanford Linear Accelerator Center in California. The discovery of this particle was so surprising that Nobel laureate Isidor Isaac Rabi exclaimed: "Who ordered that?" The average sea level muon flux (or concentration) is about one muon per square centimetre per minute.Īmerican physicists Carl Anderson and Seth Neddermeyer were studying cosmic rays when they discovered the muon in 1936. ![]() Muons make up more than half of the cosmic radiation at sea level, the remainder being mostly electrons, positrons and photons. It can be created in cosmic rays at different heights above the earth. Muons have mass 207 times larger than electrons and a lifetime of 2.20 microseconds. Muons and tauons are heavier and highly unstable versions of the electron. The best known electrically charged leptons are: We have experimental evidence for six different kinds of leptons – three negatively electrically charged leptons, and three electrically neutral. ![]() Leptons, on the other hand, can be individually observed. Quarks, at least in normal circumstances, exist only in bound states. Leptons do not take part in the strong interaction, and only interact via the electromagnetic and weak forces. Quarks bind together through the strong interaction to make, for example, protons and neutrons. electron-like particles called leptons.The so-called Standard Model of Particle Physics, which is strongly supported by extensive experimental results, suggests the material universe is assumed to be built by a small number of fundamental particles: In turn, protons and neutrons are made up of point-like particles called the "up" and "down" quarks.Īs far as we know electrons are elementary particles that is, they appear to be point-like particles without internal structure. Nuclei are made up of protons and neutrons. Matter is made up of atoms, and atoms are made of electrons and nuclei, bound by the electromagnetic force.Įlectrons have negative electric charge and their mass is small in comparison to that of the nuclei. So what are leptons? First, let's start with the basics. ![]()
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