The Speakon is a trademarked name for an electrical connector manufactured by Neutrik used in professional audio systems for connecting loudspeakers to amplifiers. Other manufacturers make compatible products under the name "speaker twist connector". Speakon connectors are rated for at least 30A RMS continuous current, higher than 1/4-inch TS phone connectors, two-pole twist lock, XLR connectors for loudspeakers. A Speakon connector is designed with a locking system that may be designed for soldered or screw-type connections. Line connectors mate with panel connectors and a cable will have identical connectors at both ends. If it is needed to join cables, a coupler can be used; the manufacturer has introduced a new series called STX which includes male line connectors and female panel connectors. Speakon connectors are designed to be unambiguous in their use in speaker cables. With 1/4" speaker jacks and XLR connections, it is possible for users to erroneously use low-current shielded microphone or instrument cables in a high-current speaker application.
Speakon cables are intended for use in high current audio applications. Speakon connectors arrange their contacts in two concentric rings, with the inner contacts named +1, +2, etc. and the outer contacts connectors. Named −1, −2, etc; the phase convention is that positive voltage on the + contact causes air to be pushed away from the speaker. Speakon connectors are made in two and eight-pole configurations; the two-pole line connector will mate with the four-pole panel connector, connecting to +1 and −1. The eight-pole connector is physically larger to accommodate the extra poles; the four-pole connector is the most common at least from the availability of ready-made leads, as it allows for things like bi-amping without two separate cables. The eight-pole connector could be used for tri-amping, or quad-amping. Another use for the four-pole cable is to carry two channels of amplified signal from an amplifier to a pair of loudspeakers using a'combiner' Y-lead connected to the two output channels, a'splitter' Y-lead to feed the loudspeakers.
The'combiner' and'splitter' Y-leads are the same: two two-pole connectors on one end, connected to the ±1 and ±2 pins of a four-pole line connector at the other end. Some amplifiers and mixer-amplifiers are configured to do this without the need for a'combiner'. Available are 2-pole "combo" receptacles that can accept 4-pole cables and 1/4″ phone plugs. PowerCon Neutrik website
Phone connector (audio)
A phone connector known as phone jack, audio jack, headphone jack or jack plug, is a family of electrical connectors used for analog audio signals. The phone connector was invented for use in telephone switchboards in the 19th century and is still used; the phone connector is cylindrical in shape, with a grooved tip to retain it. In its original audio configuration, it has two, three and five contacts. Three-contact versions are known as TRS connectors, where T stands for "tip", R stands for "ring" and S stands for "sleeve". Ring contacts are the same diameter as the sleeve, the long shank. Two-, four- and five- contact versions are called TS, TRRS and TRRRS connectors respectively; the outside diameter of the "sleeve" conductor is 6.35 millimetres. The "mini" connector has a diameter of 3.5 mm and the "sub-mini" connector has a diameter of 2.5 mm. Specific models, connectors used in specific applications, may be termed e.g. stereo plug, headphone jack, microphone jack, aux input, etc. The 3.5 mm versions are called mini-phone, mini-stereo, mini jack, etc.
In the UK, the terms jack plug and jack socket are used for the respective male and female phone connectors. In the US, a stationary electrical connector is called a jack; the terms phone plug and phone jack are sometimes used to refer to different genders of phone connectors, but are sometimes used to refer to RJ11 and older telephone plugs and the corresponding jacks that connect wired telephones to wall outlets. Phone plugs and jacks are not to be confused with the similar terms phono plug and phono jack which refer to RCA connectors common in consumer hi-fi and audiovisual equipment; the 3.5 mm connector is, sometimes—but counter to the connector manufacturers' nomenclature—referred to as mini phono. Modern phone connectors are available in three standard sizes; the original 1⁄4 inch version descends from as early as 1877, when the first-ever telephone switchboard was installed at 109 Court Street in Boston in a building owned by Charles Williams, Jr.. The 1877 switchboard was last known to be located in the lobby of Boston.
In February 1884, C. E. Scribner was issued US Patent 293,198 for a "jack-knife" connector, the origin of calling the receptacle a "jack". Scribner was issued U. S. Patents 262,701, 305,021, 489,570 relating to an improved design that more resembles the modern plug; the current form of the switchboard-plug was patented prior to 1902, when Henry P. Clausen received a patent on an improved design, it is today still used on mainstream musical equipment on electric guitars. Western Electric was the manufacturing arm of the Bell System, thus originated or refined most of the engineering designs, including the telephone jacks and plugs which were adopted by other industries, including the U. S. Military. By 1907, Western Electric had designed a number of models for different purposes, including: Code No. 47 2-conductor plugs for use with type 3, 91, 99, 102, 103, 108, 124 jacks--used for switchboards Code No. 85 3-conductor plugs for use with type 77 jacks--used for the operator's head telephone Code No. 103 twin 2-conductor plugs for use with type 91, type 99 jacks--used for the operator's head telephone and chest transmitter Code No. 109 3-conductor plugs for use with jack 92 on telephone switchboards Code No.
110, 3-conductor plug for use with jacks 49, 117, 118, 140, 141 on switchboards Code No. 112, twin 2-conductor plug for use with jacks 91 and 99--used for the operator's head telephone and chest, with a transmitter cutout key Code No. 116, 1-conductor plug for use with cordless jack boxes Code No. 126, 3-conductor plug for use with type 132 and type 309 jacks on portable street railway setsBy 1950, the two main plug designs were: WE-309, for use on high-density jack panels such as the 608A WE-310 Several modern designs have descended from those earlier versions: B-Gauge standard BPO316 EIA RS-453: Dimensional and Electrical Characteristics Defining Phone Plugs & Jacks standard of 0.206 in diameter found in IEC 60603-11:1992--Connectors for frequencies below 3 MHz for use with printed boards - Part 11: Detail specification for concentric connectors. U. S. military versions of the Western Electric plugs were specified in Amendment No.1, MIL-P-642, included: M642/1-1 M642/1-2 M642/2-1 M642/2-2 M642/4-1 M642/4-2 MIL-P-642/2 known as PJ-051.
MIL-P-642/5A: Plug and Accessory Screws, MIL-DTL-642F: Plugs and Accessory Screws, with 0.206 in diameter known by the earlier Signal Corps PL-68 designation. These are used as the microphone jack for aviation radios, on Collins S-line and many Drake amateur radios. MIL-DTL-642F states, "This specification covers telephone plugs used in telephone and teletype circuits, for connecting headsets and microphones into communications circuits." The 3.5 mm or miniature size was designed in the 1950s as two-conductor connectors for earpieces on transistor radios, remains a standard still used today. This half-sized
The XLR connector is a style of electrical connector found on professional audio and stage lighting equipment. The connectors have between three and seven pins, they are most associated with balanced audio interconnection, including AES3 digital audio, but are used for lighting control, low-voltage power supplies, other applications. XLR connectors are available from a number of manufacturers and are covered by an international standard for dimensions, IEC 61076-2-103, they are superficially similar to the smaller DIN connector range, but are not physically compatible with them. A smaller version, the Mini XLR Connector, is used on smaller equipment; the XLR connector was invented by James H. Cannon, founder of Cannon Electric in Los Angeles and for this reason it was sometimes colloquially known as a Cannon plug or Cannon connector. Manufactured as the Cannon X series, by 1950 a latching mechanism was added and by 1955 a version surrounding the female contacts with a synthetic rubber polychloroprene insulation using the part number prefix XLR.
There was an XLP series which used a hard plastic insulation, but was otherwise the same. ITT Cannon manufactured XLR connectors in two locations Kanagawa and Melbourne, Australia; the Australian operation was sold to Alcatel Components in 1992 and acquired by Amphenol in 1998. ITT Cannon continues to manufacture XLR connectors in Japan; the Switchcraft corporation started manufacturing compatible connectors, followed by Neutrik. Neutrik made a number of improvements to the connector and its second-generation design had just four parts for the cable connector and eliminated the small screws used by both Cannon and Switchcraft, which were prone to working loose, falling out and becoming lost. XLR connectors are available in male and female versions in both cable and chassis mounting designs, a total of four styles; this is unusual as many other connector designs omit one of the styles. The female XLR connectors are designed to first connect pin 1, before the other pins make contact, when a male XLR connector is inserted.
With the ground connection established before the signal lines are connected, the insertion of XLR connectors in live equipment is possible without picking up external signals. The number of pins varies; as of 2016, XLR connectors are available with up to 10 pins, mini XLR connectors with up to eight. XLR connectors from different manufacturers will intermate, with the exception of six-pin models, which are available in two incompatible designs; the older Switchcraft 6 pin design adds a center pin to the standard 5 pin design, whereas the newer Neutrik design is a different pattern. The Switchcraft 6 pin female will accept a standard 5 pin male plug whereas the Neutrik 6 pin design will not. Neutrik offers connectors in both 6 pin designs; the terminology for labelling the corresponding members of a pair of mating connectors follows the usual rules for the gender of connectors: a'male' connector is the one with pins on the smallest element,'female' has corresponding receptacles. A'plug' connector enters the'socket' connector, judged by the largest element.
For most XLR, plugs are male and sockets are female. XLR are unusual as, at least in audio applications, all four combinations of male and female and sockets are common. A common misnomer is that'plugs' are free connectors and'sockets' are panel-mounted, but XLR uses many free female sockets and panel-mounted male plugs. There is a loose convention for audio work that signals are generated by equipment with male pins and transmitted to that with female receptacles. Three-pin XLR connectors are by far the most common style, are an industry standard for balanced audio signals; the great majority of professional microphones use the XLR connector. In previous years, they were used for loudspeaker connections, for instance by Trace Elliot in its bass enclosures; the XLR could accept 14 AWG wire with a current-carrying capacity of 15 amps, suitable for most loudspeakers, but they have been superseded by the Speakon connector for professional loudspeakers. The Speakon connector accepts larger wire and carries more current, it provides a better shield for the contacts, which may carry dangerous voltages when connected to an amplifier.
Three-pin XLR connectors are used to interconnect powered speakers with line-level signals. This use is seen in PA system applications and seems to be growing more common. Rechargeable devices exist; these can be found on electric powered mobility scooters. The connectors carry from 2 to 10 amps at 24 volts. An obsolete use for three-pin XLR connectors was for MIDI data on some Octave-Plateau synthesizers including the Voyetra-8; the three-pin XLR connector is used for DMX512, on lighting and related control equipment. At the budget / DJ end of the market. However, using three-pin XLR connectors for DMX512 is prohibited by section 7.1.2 of the DMX512 standard. Use of the three-pin XLR in this context firstly presents a risk of damage to the lighting equipment should an audio cable carrying 48 volt phantom power be accidentally connected, secondly encourages the use of cable following analogue audio specifications for DMX, which can lead to signal degradation and unreliable operation of the DMX network.
Four-pin XLR connectors are used in a variety of applications. They are the standard connector such as systems made by ClearCom and Telex. Two pins are
Computer hardware includes the physical, tangible parts or components of a computer, such as the cabinet, central processing unit, keyboard, computer data storage, graphics card, sound card and motherboard. By contrast, software is instructions that can be run by hardware. Hardware is so-termed because it rigid with respect to changes or modifications. Intermediate between software and hardware is "firmware", software, coupled to the particular hardware of a computer system and thus the most difficult to change but among the most stable with respect to consistency of interface; the progression from levels of "hardness" to "softness" in computer systems parallels a progression of layers of abstraction in computing. Hardware is directed by the software to execute any command or instruction. A combination of hardware and software forms a usable computing system, although other systems exist with only hardware components; the template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann.
This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, input and output mechanisms. The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus; this is referred to as the Von Neumann bottleneck and limits the performance of the system. The personal computer known as the PC, is one of the most common types of computer due to its versatility and low price. Laptops are very similar, although they may use lower-power or reduced size components, thus lower performance; the computer case encloses most of the components of the system. It provides mechanical support and protection for internal elements such as the motherboard, disk drives, power supplies, controls and directs the flow of cooling air over internal components.
The case is part of the system to control electromagnetic interference radiated by the computer, protects internal parts from electrostatic discharge. Large tower cases provide extra internal space for multiple disk drives or other peripherals and stand on the floor, while desktop cases provide less expansion room. All-in-one style designs include a video display built into the same case. Portable and laptop computers require cases. A current development in laptop computers is a detachable keyboard, which allows the system to be configured as a touch-screen tablet. Hobbyists may decorate the cases with colored lights, paint, or other features, in an activity called case modding. A power supply unit converts alternating current electric power to low-voltage DC power for the internal components of the computer. Laptops are capable of running from a built-in battery for a period of hours; the motherboard is the main component of a computer. It is a board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives as well as any peripherals connected via the ports or the expansion slots.
Components directly attached to or to part of the motherboard include: The CPU, which performs most of the calculations which enable a computer to function, is sometimes referred to as the brain of the computer. It is cooled by a heatsink and fan, or water-cooling system. Most newer CPUs include an on-die graphics processing unit; the clock speed of CPUs governs how fast it executes instructions, is measured in GHz. Many modern computers have the option to overclock the CPU which enhances performance at the expense of greater thermal output and thus a need for improved cooling; the chipset, which includes the north bridge, mediates communication between the CPU and the other components of the system, including main memory. Random-access memory, which stores the code and data that are being accessed by the CPU. For example, when a web browser is opened on the computer it takes up memory. RAM comes on DIMMs in the sizes 2GB, 4GB, 8GB, but can be much larger. Read-only memory, which stores the BIOS that runs when the computer is powered on or otherwise begins execution, a process known as Bootstrapping, or "booting" or "booting up".
The BIOS includes power management firmware. Newer motherboards use Unified Extensible Firmware Interface instead of BIOS. Buses that connect the CPU to various internal components and to expand cards for graphics and sound; the CMOS battery, which powers the memory for date and time in the BIOS chip. This battery is a watch battery; the video card, which processes computer graphics. More powerful graphics cards are better suited to handle strenuous tasks, such as playing intensive video games. An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or
A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes; these data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi. Network computer devices that originate and terminate the data are called network nodes. Nodes are identified by network addresses, can include hosts such as personal computers and servers, as well as networking hardware such as routers and switches. Two such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other. In most cases, application-specific communications protocols are layered over other more general communications protocols; this formidable collection of information technology requires skilled network management to keep it all running reliably. Computer networks support an enormous number of applications and services such as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers and fax machines, use of email and instant messaging applications as well as many others.
Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the network's size, traffic control mechanism and organizational intent. The best-known computer network is the Internet; the chronology of significant computer-network developments includes: In the late 1950s, early networks of computers included the U. S. military radar system Semi-Automatic Ground Environment. In 1959, Anatolii Ivanovich Kitov proposed to the Central Committee of the Communist Party of the Soviet Union a detailed plan for the re-organisation of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centres, the OGAS. In 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. In 1963, J. C. R. Licklider sent a memorandum to office colleagues discussing the concept of the "Intergalactic Computer Network", a computer network intended to allow general communications among computer users.
In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at Massachusetts Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections. Throughout the 1960s, Paul Baran and Donald Davies independently developed the concept of packet switching to transfer information between computers over a network. Davies pioneered the implementation of the concept with the NPL network, a local area network at the National Physical Laboratory using a line speed of 768 kbit/s. In 1965, Western Electric introduced the first used telephone switch that implemented true computer control. In 1966, Thomas Marill and Lawrence G. Roberts published a paper on an experimental wide area network for computer time sharing. In 1969, the first four nodes of the ARPANET were connected using 50 kbit/s circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, the University of Utah.
Leonard Kleinrock carried out theoretical work to model the performance of packet-switched networks, which underpinned the development of the ARPANET. His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today. In 1972, commercial services using X.25 were deployed, used as an underlying infrastructure for expanding TCP/IP networks. In 1973, the French CYCLADES network was the first to make the hosts responsible for the reliable delivery of data, rather than this being a centralized service of the network itself. In 1973, Robert Metcalfe wrote a formal memo at Xerox PARC describing Ethernet, a networking system, based on the Aloha network, developed in the 1960s by Norman Abramson and colleagues at the University of Hawaii. In July 1976, Robert Metcalfe and David Boggs published their paper "Ethernet: Distributed Packet Switching for Local Computer Networks" and collaborated on several patents received in 1977 and 1978.
In 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a token-passing network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s. By 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 400 Gbit/s were added; the ability of Ethernet to scale is a contributing factor to its continued use. Computer networking may be considered a branch of electrical engineering, electronics engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of the related disciplines. A computer network facilitates interpersonal communications allowing users to communicate efficiently and via various means: email, instant messaging, online chat, video telephone calls, video conferencing. A network allows sharing of computing resources.
Users may access and use resources provided by devices on the network, such as printing a document on a shared network printer or use of a shared storage device. A network allows sharing of files, and
The F connector is a coaxial RF connector used for "over the air" terrestrial television, cable television and universally for satellite television and cable modems with RG-6/U cable or, in older installations, with RG-59/U cable. The F connector was invented by Eric E. Winston in the early 1950s while working for Jerrold Electronics on their development of cable television. In the 1970s, it became commonplace on VHF, UHF, television antenna connections in the United States, as coaxial cables replaced twin-lead, it is now specified in IEC 60169 Radio-frequency connectors, part 24. The F connector is an inexpensive, threaded, compression connector for radio frequency signals, it has good 75 Ω impedance match for frequencies well over 1 GHz and has usable bandwidth up to several GHz. Connectors mate using a 3⁄8 in-32 unified extra fine thread; the female connector has a socket for external threads. The male connector has a center pin, a captive nut with internal threads; the design allows for low-cost construction, where cables are terminated exclusively with male connectors.
The coaxial cable center conductor forms the pin, cable dielectric extends up to the mating face of the connector. Thus, the male connector consists of only a body, crimped onto or screwed over the cable shielding braid, a captive nut, neither of which require tight tolerances. Push-on versions are available. Female connectors are used on bulkheads or as couplers being secured with the same threads as for the connectors, thus can be manufactured as a single piece, with center sockets and dielectric at the factory where tolerances can be controlled. This design is subject to the surface properties of the inner conductor and is not corrosion resistant. Hence waterproof versions are needed for outside use. Corrosion resistance can be improved by coating all bare copper wires with silicone grease; the F connector is not weatherproof. Neither the threads nor the joint between male connector body and captive nut seal. However, male connectors are enhanced with an o-ring inside the captive nut; this seals between the mating faces of both connectors, providing good waterproofing for the center conductor.
The cable and satellite television entities use compression fittings with F connectors on customer premises. In Europe, block down-converted satellite signals from LNBs and DC power and block signalling from satellite receivers are near passed through F connectors. F connectors are the most suitable for domestic terrestrial and satellite TV installations where the delivery of high frequency information is required. Belling-Lee connectors are not well suited for long-haul building delivery of frequencies above 500 MHz, because the standard was designed around tube receivers and mediumwave antennas. F connectors require more care to properly install the male connectors to the cable than the Belling-Lee type, with the exception of compression or flex type connections. Push-on F connectors provide poorer shielding against microwave signals of high field strength; this leakage problem is more an artifact of bent or broken push on connectors, but is not observed with compression connectors. Nearby television, FM radio, mobile & cordless phones, government radiolocation transmitters can interfere with a CATV or DTH Satellite reception or operation if the Flex connector poorly installed.
Belling-Lee connector Coaxial cable Component video Composite video Diplexer RCA connector Satellite dish TV aerial plug MCX connector Compression Tool for crimping Antenna-cables&connectors
The BNC connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. The interface specifications for the BNC and many other connectors are referenced in MIL-STD-348, it features two bayonet lugs on the female connector. BNC connectors are used with miniature-to-subminiature coaxial cable in radio and other radio-frequency electronic equipment, test instruments, video signals; the BNC was used for early computer networks, including ARCnet, the IBM PC Network, the 10BASE2 variant of Ethernet. BNC connectors are made to match the characteristic impedance of cable at either 75 ohms, they are applied for frequencies below 4 GHz and voltages below 500 volts. Similar connectors using the bayonet connection principle exist, a threaded connector is available. United States military standard MIL-PRF-39012 entitled Connectors, Radio Frequency, General Specification for covers the general requirements and tests for radio frequency connectors used with flexible cables and certain other types of coaxial transmission lines in military and spaceflight applications.
The BNC was designed for military use and has gained wide acceptance in video and RF applications to 2 GHz. The BNC uses some plastic dielectric on each gender connector; this dielectric causes increasing losses at higher frequencies. Above 4 GHz, the slots may radiate signals, so the connector is usable, but not stable up to about 11 GHz. Both 50 ohm and 75 ohm versions are available; the BNC connector is used for signal connections such as: analog and serial digital interface video signals radio antennas aerospace electronics nuclear instrumentation test equipment. The BNC connector is used for composite video on commercial video devices. Consumer electronics devices with RCA connector jacks can be used with BNC-only commercial video equipment by inserting an adapter. BNC connectors were used on 10base2 thin Ethernet network cables and network cards. BNC connections can be found in recording studios. Digital recording equipment uses the connection for synchronization of various components via the transmission of word clock timing signals.
The male connector is fitted to a cable, the female to a panel on equipment. Cable connectors are designed to be fitted by crimping using a special power or manual tool. Wire strippers which strip outer jacket, shield braid, inner dielectric to the correct lengths in one operation are used; the connector was named the BNC after its bayonet mount locking mechanism and its inventors, Paul Neill and Carl Concelman. Neill worked at Bell Labs and invented the N connector. A backronym has been mistakenly applied to it: British Naval Connector. Another common incorrectly attributed; the basis for the development of the BNC connector was the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering of the University of Pennsylvania. In 1945, while working at Hazeltine Electronics Corporation, he filed a patent for a connector for coaxial cables that would minimize wave reflection/loss; the patent was granted in 1951. BNC connectors are most made in 50 and 75 ohm versions, matched for use with cables of the same characteristic impedance.
The 75 ohm types can sometimes be recognized by the reduced or absent dielectric in the mating ends but this is by no means reliable. There was a proposal in the early 1970s for the dielectric material to be coloured red in 75 ohm connectors, while this is implemented, it did not become standard; the 75 ohm connector is dimensionally different from the 50 ohm variant, but the two can be made to mate. The 50 ohm connectors are specified for use at frequencies up to 4 GHz and the 75 ohm version up to 2 GHz. A 95 ohm variant is used within the aerospace sector, but elsewhere, it is used with the 95 ohm video connections for glass cockpit displays on some aircraft. Video and DS3 Telco central office applications use 75 ohm BNC connectors, whereas 50 ohm connectors are used for data and RF. Many VHF receivers used 75 ohm antenna inputs, so they used 75 ohm BNC connectors. Reverse-polarity BNC is a variation of the BNC specification which reverses the polarity of the interface. In a connector of this type, the female contact found in a jack is in the plug, while the male contact found in a plug is in the jack.
This ensures that reverse polarity interface connectors do not mate with standard interface connectors. The SHV connector is a high-voltage BNC variant. Smaller versions of the BNC connector, called Mini BNC and High Density BNC, are manufactured by Amphenol. While retaining the electrical characteristics of the original specification, they have smaller footprints giving a higher packing density on circuit boards and equipment backplanes; these connectors have true 75 ohm impedance making them suitable for HD video applications. The different versions are designed to mate with each other, a 75 ohm and a 50 ohm BNC connector which both comply with the 2007 IEC standard, IEC 60169-8, will mate non-destructively. At least one manufacturer claims high reliability for the connectors' compatibility. At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects. BNC connectors were thus made only in 50 ohm