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Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work on the standard began in 1980 at Bell Labs and was formally standardized in 1988 in the CCITT "Red Book". By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use. ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance.
A soldering iron is a hand tool used in soldering. It supplies heat to melt solder so that it can flow into the joint between two workpieces.
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow.
Solder is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to adhere to and connect the pieces after cooling, which requires that an alloy suitable for use as solder have a lower melting point than the pieces being joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics.
Digital subscriber line is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access.
Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field.
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. In contrast to a diode however, it has the same characteristic for both directions of traversing current. Traditionally, varistors were indeed constructed by connecting two rectifiers, such as the copper-oxide or germanium-oxide rectifier in antiparallel configuration. At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV).
An electrical connector is an electromechanical device used to join electrical conductors and create an electrical circuit. Most electrical connectors have a gender – i.e. the male component, called a plug, connects to the female component, or socket. The connection may be removable, require a tool for assembly and removal, or serve as a permanent electrical joint between two points. An adapter can be used to join dissimilar connectors.
The reed switch is an electrical switch operated by an applied magnetic field. It was invented in 1922 by professor Valentin Kovalenkov at Leningrad Electrotechnical University, and later evolved at Bell Telephone Laboratories in 1936 by Walter B. Ellwood into the reed relay. In its simplest and most common form, it consists of a pair of ferromagnetic flexible metal contacts in a hermetically sealed glass envelope. The contacts are usually normally open, closing when a magnetic field is present, or they may be normally closed and open when a magnetic field is applied. The switch may be actuated by an electromagnetic coil, making a reed relay, or by bringing a permanent magnet near it. When the magnetic field is removed, the contacts in the reed switch return to their original position. The "reed" is the metal part inside the reed switch envelope that is relatively thin and wide to make it flexible. It somewhat resembles part of some reed plants. The term "reed" may also include the external wire lead as well as the internal part.
In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.
Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures. As the structure size in electronics such as integrated circuits (ICs) decreases, the practical significance of this effect increases.
An electrical contact is an electrical circuit component found in electrical switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, typically metal. When a pair of contacts touch, they can pass an electrical current with a certain contact resistance, dependent on surface structure, surface chemistry and contact time; when the pair is separated by an insulating gap, then the pair does not pass a current. When the contacts touch, the switch is closed; when the contacts are separated, the switch is open. The gap must be an insulating medium, such as air, vacuum, oil, SF6. Contacts may be operated by humans in push-buttons and switches, by mechanical pressure in sensors or machine cams, and electromechanically in relays. The surfaces where contacts touch are usually composed of metals such as silver or gold alloys that have high electrical conductivity, wear resistance, oxidation resistance and other properties.
A hermetic seal is any type of sealing that makes a given object airtight. The term originally applied to airtight glass containers, but as technology advanced it applied to a larger category of materials, including rubber and plastics. Hermetic seals are essential to the correct and safe functionality of many electronic and healthcare products. Used technically, it is stated in conjunction with a specific test method and conditions of use.
The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance. This effect is described by the term electrical contact resistance (ECR) and arises as the result of the limited areas of true contact at an interface and the presence of resistive surface films or oxide layers. ECR may vary with time, most often decreasing, in a process known as resistance creep. The idea of potential drop on the injection electrode was introduced by William Shockley to explain the difference between the experimental results and the model of gradual channel approximation. In addition to the term ECR, interface resistance, transitional resistance, or just simply correction term are also used. The term parasitic resistance is used as a more general term, of which it is usually assumed that contact resistance is a major component.
Glass-to-metal seals are a very important element of the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass encapsulated semiconductor diodes, reed switches, pressure tight glass windows in metal cases, and metal or ceramic packages of electronic components.
Soldering is a process in which two or more items are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces. In brazing, the work piece metal also does not melt, but the filler metal is one that melts at a higher temperature than in soldering. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes.
Electronic components have a wide range of failure modes. These can be classified in various ways, such as by time or cause. Failures can be caused by excess temperature, excess current or voltage, ionizing radiation, mechanical shock, stress or impact, and many other causes. In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits.
Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor.
Contact protection methods are designed to mitigate the wear and degradation occurring during the normal use of contacts within an electromechanical switch, relay or contactor and thus avoid an excessive increase in contact resistance or switch failure.
Ragnar Holm, was a Swedish physicist and researcher in electrical engineering, who was partially active in Germany and the United States.
References
- ↑ McMillan, Gregory K., ed. (1999). Process/Industrial Instruments and Controls Handbook (5th ed.). McGraw Hill. p. 7.26. ISBN 0-07-012582-1.
- ↑ "Switch Contact Design - Switches - Electronics Textbook".
- ↑ Zhai, C.; Hanaor, D.; Proust, G.; Gan, Y. (2015). "Stress-Dependent Electrical Contact Resistance at Fractal Rough Surfaces" (PDF). Journal of Engineering Mechanics. 143 (3): B4015001. doi:10.1061/(ASCE)EM.1943-7889.0000967.
- 1 2 "Relay contact life" (Application note). Winston-Salem, NC, USA: Tyco Electronics Corporation (TEC), P&B Relays. 13C3236, IH/12-00. Archived from the original on 2018-05-19. Retrieved 2018-05-18.
- ↑ Mairs, William (September 2004). "Keeping in contact" (PDF). NHP Technical News. NHP Electrical Engineering Products Pty. (42). TNL-42 10/04 14M. Archived (PDF) from the original on 2018-05-19. Retrieved 2018-05-19.
- ↑ Stewart, Anthony (2011). "The Case of the Intermittent Relay". Design News .
- ↑ Recommendation G.992.3: Asymmetric digital subscriber line transceivers 2 (ADSL2). ITU-T. Archived from the original on 2018-05-19. Retrieved 2018-05-19.
- ↑ Bennett, Brad (1996-12-13). "Sealing current on ISDN loops". comp.dcom.isdn. Retrieved 2018-05-19.
[…] Wynn Quon: The Bellcore Layer 1 specs talk about "sealing current". This is a low current (1-20mA) DC signal applied to tip and ring. […] It is supposed to reduce oxidation at line splices and it provides a troubleshooting aid in the field. […] Brad Bennett: I was personally the researcher that did the sealing current work while at Bellcore […] sealing current does effectively keep a copper loop intact (through a process called electromigration […] it does work on copper loops which have splices […] for direct copper loops (CO to customer sites) it is ALWAYS suppose to be applied (and is built into the line cards). For other technologies (e.g. BRITE cards), which synthesize ISDN from 3 DS0 circuits at a subscriber loop cabinet (SLC), I am […] not sure it is a requirement. […] other interesting upshots of […] this work, which I am not certain have ever made it to the public. For example there are certain metal pairs [for] which you definitely do NOT want to use sealing current […] or […] run any continuous DC current (e.g. copper and precious metals). Such contacts (splices) are materially designed to fail if current continually flows in the wrong direction. […] on […] copper wires, sealing current helps to maintain good electrical connections […]
- ↑ Kiameh, Philip (2003-04-11). Electrical Equipment Handbook : Troubleshooting and Maintenance: Troubleshooting and Maintenance. McGraw Hill Professional. pp. 13–9. ISBN 978-0-07-139603-5.
- ↑ "Down and Dirty with Contact Cleaners". 2017-02-17.
