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| A '''[[destroyer]]''' is a type of warship, the nature of which has evolved since it first came into use, roughly at the beginning of the twentieth century. Several other warship designations have, at different times and in different navies, overlapped the "destroyer" role. Most common among these roles are cruiser and ocean escort. Another type of vessel, whose nomenclature is the root of "destroyer", has been called "torpedo boat" and exists in new forms generically called fast attack craft.
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| ====Initial usage====
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| When the modern self-propelled torpedo was invented, in 1866, by Robert Whitehead, it was initially added to conventional warships, but navies soon realized that a small, fast craft, with a main battery of torpedoes, could threaten much larger warships such as battleships. The battleship of the early 20th century was the largest, most heavily armed, and most heavily protected warship type, but relatively slow and not extremely maneuverable. Torpedo boats were generally not capable of long-range steaming or being seaworthy in the "blue water" deep ocean; they were coastal craft.
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| When battleships and other large ships, possibly escorting unarmed cargo and troop transports, needed to approach a hostile shore, they needed to deal with the torpedo boat threat. A partial solution was adding a secondary gun battery of smaller caliber, faster firing rate, and faster aiming than the main guns intended to sink other battleships, but the secondary battery still let the torpedo boats come too close.
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| [[Image:Spanish TBD Audaz, 1898.jpg|thumb|300px|left|Hybrid sail-steam Spanish torpedo boat destroyer ''Audaz]]
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| A new type of vessel, called the "torpedo boat destroyer", was developed as an escort to major warships, and possibly merchant vessels threatened by torpedo boats. In the words of a requirement restated a century later, "Self-deployability (blue water endurance) is needed to allow the platforms to get to the contested area without the need for valuable and scarce open ocean transport or the support of an ever-present mothership." Such vessels still had to be small, fast, and maneuverable enough to pursue and destroy torpedo boats.</onlyinclude> Early approaches to increasing range and self-deployability included the use of sails in addition to steam, on the Spanish torpedo boat destroyer ''Audaz'', in service between 1897 and 1927.
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| It soon became obvious that the torpedo boat destroyer was a useful vessel for a wide range of applications, such as convoy escort, so the specialized designation became the simple "destroyer". Ironically, while the first destroyers were armed only with quick-firing guns, usually of several calibers from medium to light, navies started equipping destroyers with torpedoes, as the weapon of choice if they did need to confront battleships. For simplicity, the category of "cruiser" is not being included in this immediate discussion; simply assume they were vessels of intermediate characteristics between battleships and destroyers.
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| The new destroyers would usually make torpedo attacks in groups. Such groups would often be built around a light cruiser or a ship called a destroyer leader; both types were more survivable and more heavily armed than destroyers, which better fitted them to lead the attack unit. Early destroyers were intended to be small and inexpensive, with numbers of hulls being more important than individual ship capability.
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| ====First World War, and a new torpedo threat====
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| [[Image:USS Bainbridge (DD-246).jpg|thumb|350px|''USS Bainbridge'' (DD-246), last class before breaking away from WWI "four stack flush deck" design]]
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| The pure torpedo boat was becoming less popular around the start of the First World War, although variants would keep returning. Torpedoes, however, were still a real threat, but from submarines rather than surface vessels.
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| Technology for finding submerged submarines lagged the introduction of the undersea weapons, and was quite primitive and short-ranged. In general, the first antisubmarine sensors were passive listening devices, called "hydrophones". Putting hydrophones on many destroyers allowed an antisubmarine screen to be formed around the "high-value assets", the vessels the submarines had as primary targets.
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| Once a submerged submarine was located, location being a very loose term at the time, the destroyer needed some way to attack it. Clearly, guns that could blow a surface torpedo boat out of the water were not the answer, since they cannot shoot at underwater targets. The first antisubmarine weapons were depth charges, or containers of explosives that would be dropped, from the surface, over the location of a suspected submarine, and would detonate when they reached a preset depth. The submarine's depth was even harder to determine than its range and bearing from the destroyer; it was estimated based on the strength of the sound, knowledge of the bottom depth and water characteristics, and a seaman's judgment. Since the submarine's position was poorly defined, large explosive charges were needed to have a chance of damage with other than a lucky direct hit.
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| By 1918, however, an active sound-based technique, code-named ASDIC for an apparently nonexistent "Allied Submarine Detection Investigation Committee" was mounted on several British and U.S. destroyers. It came too late for combat use in the First World War, but development actively continued. The more common term became sonar, for "sound detection and ranging". In modern intelligence terminology, active and passive sound-based systems were the acoustic MASINT or acoustic intelligence of geophysical measurement and signal intelligence.
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| ''[[Destroyer|.... (read more)]]''
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Categories of smart home devices shown on Amazon's website in April 2023.
The phrase smart home refers to home automation devices that have internet access. Home automation, a broader category, includes any device that can be monitored or controlled via wireless radio signals, not just those having internet access. Whether the device is powered by the electrical grid or by battery, if it uses the home Wi-Fi network and if an internet logon needs to be created to use it, then it is smart home technology.
Collectively, all the smart home devices on every home's Wi-Fi network helps to make up what is called the Internet of Things (IoT), a huge sea of sensors and control devices across the world that are capable of being accessed from afar via the internet. One of the key reasons such devices need internet access is so that the manufacturer can periodically download updated firmware to the device to keep it up-to-date. However, being available via the internet also means that such devices are, potentially, available for spying or hacking. Today, homes may contain dozens or even hundreds of such devices, and consumers may enjoy their benefits while knowing little about how they work, or even realizing that they are present.
Not all home automation is "smart"
Many remotely controllable devices do not require internet access. They may instead have physical control devices that use either RF (“Radio Frequency”) or IR (“Infrared”) beams, two different kinds of energy used in remote controls to communicate commands. Non-"smart" home automation may also present security risks, because the control signals can be hijacked by bad actors with the right signaling equipment. Garage door openers are of particular note in this regard. Modern automobiles, in fact, are full of automation similar to home automation, and cars are hackable by bad actors in a number of ways. See Wikipedia's Automotive hacking article for more information.
Incompatibility hassles
At present, consumers must make sure that the smart device they wish to use is specified to be compatible whichever phone/tablet operating system they use (Apple vs. Android). Since smart home products emerged in the absence of any standard, a morass of competing methods for networking, control and monitoring now exist. For some products, consumers may need to buy an expensive hub, or bridge, a device that is specific to one vendor. Products made by different manufacturers but performing the same function are typically not interoperable. Consumers often need to open a different app on their smartphone or tablet in order to control devices by each manufacturer. This may make it too expensive and awkward to try out competing devices, leaving consumers stuck with the product they bought originally or else having to add yet more apps to their phones.
Security concerns
Security for smart home products has been uneven and sometimes seriously inadequate. Smart thermostats which can monitor whether a home's occupants are present or not, entry-way locks, robotic vacuums that work with a map of the house, and other smart home devices can present very real dangers if hackers can access their data.
Matter, an emerging standard
Matter is emerging standard in 2023 intended to increase security, reliability and inter-operability of smart-home devices. About ten years ago, industry consortiums formed to work on standards for smart home device communications, and their underlying wireless communications, which would make it possible for products from all vendors to work together seamlessly and provide fast performance, privacy, and security and would work even if there is not connection to the outside internet (i.e., no connection to "the cloud" or to servers).
