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Doorbells
A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button, the bell rings inside the building, alerting the occupant to the presence of the visitor. Although the first doorbells were mechanical, activated by pulling a cord connected to a bell, modern doorbells are electric, operated by a pushbutton switch. Modern doorbells often incorporate intercoms and miniature video cameras to increase security. History William Murdoch, a Scottish inventor, installed a number of his own innovations in his house, built in Birmingham in 1817; one of these was a loud doorbell, that worked using a piped system of compressed air. A precursor to the electric doorbell, specifically a bell that could be rung at a distance via an electric wire, was invented by Joseph Henry around 1831. By the early 1900s, electric doorbells had become commonplace. Wired doorbells In most wired systems, a button on the outside next to the door, loca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doorbell Shop Netherlands
A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button, the bell rings inside the building, alerting the occupant to the presence of the visitor. Although the first doorbells were mechanical, activated by pulling a cord connected to a bell, modern doorbells are electric, operated by a pushbutton switch. Modern doorbells often incorporate intercoms and miniature video cameras to increase security. History William Murdoch, a Scottish inventor, installed a number of his own innovations in his house, built in Birmingham in 1817; one of these was a loud doorbell, that worked using a piped system of compressed air. A precursor to the electric doorbell, specifically a bell that could be rung at a distance via an electric wire, was invented by Joseph Henry around 1831. By the early 1900s, electric doorbells had become commonplace. Wired doorbells In most wired systems, a button on the outside next to the door, locate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury Switch
A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. There are several different basic designs (tilt, displacement, radial, etc.) but they all share the common design strength of non-eroding switch contacts. The most common is the ''mercury tilt switch''. It is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction. This is what older style thermostats used to turn a heater or air conditioner on or off. The ''mercury displacement switch'' uses a 'plunger' that dips into a pool of mercury, raising the level in the container to contact at least one electrode. This design is used in relays in industrial applications that need to switch high current loads frequently. These relays use electromagnetic coils to pull steel sleeves inside hermetically sealed containers. Description Mercury ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Box
A bell box is an audible device, often electric, which when activated, emits a chime, bell, or buzzer sound. Components The housing of the bell box may be manufactured from wood, metal, or plastic. The basic core component of a conventional bell box is an electromagnet and a bell or other metal part, some of which create a repetitive sound. The bell sound is normally created inside the box, although the unit may have bells mounted on the outside of the box. The bell box may also include visual alerts such strobe or other flashing lights. Types A doorbell uses a bell box to signal the occupant of a home or business. A bell box for early telephones is commonly known as a ringer box. , Telephony Museum Web Site. Other types of bell boxes include |
Terminal (electronics)
A terminal is the point at which a conductor from a component, device or network comes to an end. ''Terminal'' may also refer to an electrical connector at this endpoint, acting as the reusable interface to a conductor and creating a point where external circuits can be connected. A terminal may simply be the end of a wire or it may be fitted with a connector or fastener. In network analysis, ''terminal'' means a point at which connections can be made to a network in theory and does not necessarily refer to any physical object. In this context, especially in older documents, it is sometimes called a pole. On circuit diagrams, terminals for external connections are denoted by empty circles. They are distinguished from nodes or junctions which are entirely internal to the circuit, and are denoted by solid circles. All electrochemical cells have two terminals (electrodes) which are referred to as the anode and cathode or positive (+) and negative (-). On many dry batteries, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Light
An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the socket of a light fixture, which is often called a "lamp" as well. The electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap. The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, such as fluorescent lamps, and LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor. Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. Vasily Vladimirovich Petrov developed the first persistent electric arc in 1802 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hearing Loss
Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in loneliness. Deaf people usually have little to no hearing. Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear, and certain medications or toxins. A common condition that results in hearing loss is chronic ear infections. Certain infections during pregnancy, such as cytomegalovirus, syphilis and rubella, may also cause hearing loss in the ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Westminster Quarters
The Westminster Quarters, from its use at the Palace of Westminster, is a melody used by a set of four quarter bells to mark each quarter-hour. It is also known as the Westminster Chimes, Cambridge Quarters or Cambridge Chimes from its place of origin, the Church of St Mary the Great, Cambridge. Description The Westminster Quarters are sounded by four quarter bells hung next to Big Ben in the Elizabeth Tower belfry in the Palace of Westminster. These are: The quarters consist of five changes, combinations of the four pitches provided by these quarter bells ( G4, F4, E4, B3) in the key E major. This generates five unique changes as follows: # G4, F4, E4, B3 # E4, G4, F4, B3 # E4, F4, G4, E4 # G4, E4, F4, B3 # B3, F4, G4, E4 Each of the five changes is played as three crotchets (quarter note) and a minim (half note) and are always played in the sequence 1, 2, 3, 4, 5. This sequence of five changes is used twice every hour as follows: :First quarter, change 1. :Half hou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tubular Bells
Tubular bells (also known as chimes) are musical instruments in the percussion family. Their sound resembles that of church bells, carillon, or a bell tower; the original tubular bells were made to duplicate the sound of church bells within an ensemble.James Blades and James Holland. "Tubular bells". Grove Music Online. Oxford Music Online. Oxford University Press, accessed August 18, 2015Oxfordmusiconline.com/ref> Each bell is a metal tube, in diameter, tuned by altering its length. Its standard range is C4–F5, though many professional instruments reach G5. Tubular bells are often replaced by studio chimes, which are a smaller and usually less expensive instrument. Studio chimes are similar in appearance to tubular bells, but each bell has a smaller diameter than the corresponding bell on tubular bells. Tubular bells are sometimes struck on the top edge of the tube with a rawhide- or plastic-headed hammer. Often, a sustain pedal will be attached to allow extended ringing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spring (device)
A spring is an elastic object that stores mechanical energy. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel, although some non-metallic objects like the bow are also springs. When a conventional spring, without stiffness variability features, is compressed or stretched from its resting position, it exerts an opposing force approximately proportional to its change in length (this approximation breaks down for larger deflections). The ''rate'' or ''spring constant'' of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring's rate is expressed in units of force divided by distance, for example or N/m or lbf/in. A torsion spring is a spring that works by twisting; when it is twisted about its axis by an angle, it produc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solenoid
upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field. The coil can produce a uniform magnetic field in a volume of space when an electric current is passed through it. The term ''solenoid'' was coined in 1823 by André-Marie Ampère. The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (not unlike an arc spring). Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons. Electrons take helical paths within the magnetic field. These solenoids, focus coils, surround nearly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground (electricity)
In electrical engineering, ground or earth is a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth. Electrical circuits may be connected to ground for several reasons. Exposed conductive parts of electrical equipment are connected to ground, to protect users from electrical shock hazard. If internal insulation fails, dangerous voltages may appear on the exposed conductive parts. Connecting exposed parts to ground will allow circuit breakers (or RCDs) to interrupt power supply in the event of a fault. In electric power distribution systems, a protective earth (PE) conductor is an essential part of the safety provided by the earthing system. Connection to ground also limits the build-up of static electricity when handling flammable products or electrostatic-sensitive devices. In some telegraph and power transmission circuits, the ground itself can be used as one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standby Power
Standby power, also called vampire power, vampire draw, phantom load, ghost load or leaking electricity ("phantom load" and " leaking electricity" are defined technical terms with other meanings, adopted for this different purpose), refers to the way electric power is consumed by electronic and electrical appliances while they are switched off (but are designed to draw some power) or in standby mode. This only occurs because some devices claimed to be "switched off" on the electronic interface, but are in a different state. Switching off at the plug, or disconnecting from the power point, can solve the problem of standby power completely. In fact, switching off at the power point is effective enough, there is no need to disconnect all devices from the power point. Some such devices offer remote controls and digital clock features to the user, while other devices, such as power adapters for disconnected electronic devices, consume power without offering any features (sometimes ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
