The name kreisfreie Stadt (plural: "kreisfreie Städte") is used for German towns that have their own government. This town government is independent of the government of the next-higher level of authority, the "Landkreis". Today, most of the cities that have this statute, are big cities, with 100.000 people living there, or more. The concept grew historically. That means that there are big cities, with more than 100.000 people that do not have the statute. There are also some cities who have only taken a part of the responsibilities of a Landkreis (or Kreis). The smallest city with the statute is Zweibrücken. About 35.000 people live there. The biggest of these cities is Munich, with about 1.3 million people. Hamburg and Berlin are bigger. They are city states, though. The city state of Bremen (state) is made of two "kreisfreie Städte", the city of Bremen, and the city of Bremerhaven, about 60 km to the north. About half a million people live in Bremen (1.5 million in the agglomeration), about 117.000 people live in Bremerhaven.
But not every big city with more than 100.000 inhabitants is a "kreisfreie Stadt". Some of them, for example Recklinghausen or Göttingen (both more 120.000 inhabitants) are part of a "Landkreis".
There are very few cities, who only took part of the paperwork from the Landkreis. Some of these are called "Große selbständige Stadt" (Translates to "Big sovereign city"). They only seem to exist in Lower Saxony. They are:
Celle, Cuxhaven, Goslar, Hameln, Hildesheim, Lingen, and Lüneburg. Things like hunting permits cannot be delegated to the cities. Other things, like what to do with the trash have sometimes been delegated.
Similar concepts to that of the "kreisfreie Stadt" are Unitary authorities in the United Kingdom, or that of "independent city" in the United States.
Jet aircraft
Jet aircraft are aircraft with jet engines. Unlike propeller-powered aircraft, jet aircraft normally fly at altitudes as high as 100 to 1,5 meters, about 33 to . At these altitudes, jet engines can achieve maximum efficiency over long distances. The engines in propeller powered aircraft achieve their maximum efficiency at much lower altitudes.
Egypt–Israel Peace Treaty
The Egypt–Israel Peace Treaty was a peace treaty between Egypt and Israel. It was signed by both countries in 1979, at the end of the Camp David Accords. It was the first treaty with Israel from a Middle-Eastern Arabic nation. After signing it, Egypt was removed from the Arab League.
The Egypt–Israel treaty was signed by Egyptian president Anwar Sadat and Israeli prime minister Menachem Begin, and witnessed by United States president Jimmy Carter.
Downtown
Downtown (called a city centre in British English) is a word used in North America which refers to the main part of a city. It is usually the central business district where most commercial and office areas are; many of them being in skyscrapers. Tourism also concentrates there.
IEEE 802.11
IEEE 802.11 is a series of protocols for wireless networking. Often these are called Wireless LAN, "WLAN", or Wi-Fi. Such a protocol allows computers that have the needed radio parts to communicate with each other, without a cable. There are many types of Wi-Fi standards, known as 802.11 a, b, g, n, and recently ac & ad. These specifications are different in terms of speed and how far away you can use them.
The first Wi-Fi standard was made in 1997. It is called IEEE 802.11. It allows communication with 1-2 MBit per second. Today it is outdated, and rare. Later standards add a letter to the name. They are labelled IEEE 802.11a to IEEE 802.11g. There are plans for ones labeled h, i, j, n, p and s. They are all compatible with each other.
Newer standards have a Bit rate of 54 MBit/s. About 40-50% of this is usable in real-life situations. As of 2007, the standards most widely used are IEEE 802.11g, and IEEE 802.11b.
Data communication is either done in the 2.4 GHz band or in the 5 GHz band. The 2.4 GHz band is a general use band. Microwave ovens and Bluetooth are among the things that emit radio waves in this band. The 2.4 GHz band has the problem that there are only very few channels that can be used at the same time, without the signals interfering. There are three usable channels there. When more than three networks operate in the same place, signals still get to the user correctly, but interference slows them.
The 5 GHz band can solve some of these problems, but it introduces others. That band has 19 usable channels. Overall the band is less used. However there are more regulations. Most devices need to be able to choose their channel to minimize interference. Some channels require that those participating can do Transmitter Power Control. This means they adapt the strength of the signal to what is actually needed. This helps reduce the amount of interference between different networks.
Wireless LAN
In computing, Wireless LAN (WLAN) or Wireless local area network is a term to refer to a Local Area Network that does not need cables to connect the different devices. Instead, radio waves and IEEE 802.11 are used to communicate.
Today, most technologies used for WLANs use Orthogonal Frequency Division Multiplexing. This means that several frequencies are used at the same time. Signals that are close to each other, but that belong to different channels do not disturb each other, as they use different coding schemes. Depending on the material used, it is possible to cover between 30 metres and 100 metres indoors; outdoors, the range is about 100-300m, if there are no obstacles.
Bluetooth
Bluetooth is a protocol for wireless communication over short distances. It was developed in the 1990s, to reduce the number of cables. Devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles can connect to each other, and exchange information. This is done using radio waves. It can be done securely. Bluetooth is usually only used for relatively short distances, like a few metres. Some signals can be up to 100 metres.
There are different standards. Data rates vary. Currently, they are at 1-3 MBit per second. Typical Bluetooth applications are to connect a headset to a mobile phone, or to connect a computer mouse, keyboard or printer.
Bluetooth devices use the ISM Band around 2.4 GHz. This can be used worldwide, without the need to pay license fees, but many other devices, like DECT telephones (wireless phones), smart tags with RFID, baby phones use it too. Bluetooth uses the same bands as some WLANs, but the modulation technique is different. Bluetooth uses Frequency-hopping spread spectrum.
There are many situations today where either Bluetooth or Wireless LANs can be used. Examples include setting up networks, printing or transferring files and data from a PDA to a computer. Both are versions of unlicensed wireless technology. WLANs can span bigger distances and offer higher throughput. Bluetooth does not require expensive hardware. It also needs less power to operate.
Both use the same radio frequency range, but their modulation techniques are different. Both have been developed to replace cabling. Bluetooth wanted to get rid of the peripheral equipment cables, WLANs wanted to get rid of the cables needed to set up a LAN.
Bluetooth exists in many products, such as telephones, the Wii or PlayStation 3. It has recently been built into some electronic watches, modems and headsets. The technology is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with telephones (i.e. with a Bluetooth headset) or byte data with hand-held computers (transferring files).