Relay

A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays".

Relay (shop)

Relay is a chain of newspaper, magazine, book, and convenience stores, mostly based in train stations and airports. It is owned by Lagardère Services, a subsidiary of Lagardère Group.

Its heaviest concentration is in France, but it also operates in other countries. In 2010, the network had 1,100 shops on 4 continents.

References

External links

Communications satellite

A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder; it creates a communication channel between a source transmitter and a receiver(s) at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. There are over 2,000 communications satellites in Earth’s orbit, used by both private and government organizations.

Wireless communication uses electromagnetic waves to carry signals. These waves require line-of-sight, and are thus obstructed by the curvature of the Earth. The purpose of communications satellites is to relay the signal around the curve of the Earth allowing communication between widely separated points. The electromagnetic signals that communication satellites work with, have a large spectrum of wavelengths and frequencies. To keep these waves from interfering with one another, international organizations have certain rules and regulations describing which wavelength a certain company or group can use. By separating out wavelengths, communication satellites will have minimal interference and be able to communicate effectively.

Hydro

Hydro may refer to:

Energy technologies

Utilities

Australia:

Canada:

Europe:

Other uses

Places:

Personal names:

Hydro (fuel-station chain)

Hydro was a chain of fuel stations throughout Sweden owned by Statoil. The chain had more than 500 stations, as well as some unmanned Uno-X stations. The company also operated in retailing natural gas, electricity and heating oil.

History

The Hydro chain was created in the late 1980s when Norsk Hydro bought the Mobil stations in Norway, Sweden and Denmark to transform itself to a vertically integrated petroleum company. The stations were rebranded Hydro in all three countries. In 1995 the Norwegian and Danish stations were converted to Hydro Texaco when Hydro merged its stations in the two countries with Texaco's stations. In 2007 the ownership of Hydro was transferred to StatoilHydro when Norsk Hydro's oil and gas division merged with Statoil. When StatoilHydro was renamed Statoil in November 2009, the use of the Hydro-brand was discontinued and ownership of the Hydro filling stations was transferred to St1.

References

External links

List of Marvel Comics characters: H

Haazareth Three

The Haazareth Three debuted in Fantastic Four Vol 3 #69 (2003). They operate out of the hellish realm ruled by Mephisto. They are a trio of demons with whom Doctor Doom made a pact (seen in the Unthinkable story arc). They made a deal with Doom; if he sacrifices something of irreplaceable value, they would provide him with the magical powers he would have possessed if he had chosen to devote his life to studying magic over science. Doom does, killing his childhood sweetheart, Valeria. The demons come through with the deal.

Hack

Hack is a mutant whose first appearance was in Excalibur vol. 2 #2. He was one of the few survivors after Cassandra Nova programmed her Wild Sentinels to decimate the island nation of Genosha, killing over 16 million mutants. He found other survivors and allied himself with Unus the Untouchable and his gang. He was a very valuable asset on the island since all forms of electronic communication were eradicated or made useless by the resulting electro-magnetic damage. Inside of the gang, he became close friends with Hub and the two of them began to doubt if Unus' exclusive, clique-like strategy was the best way. Hack was gifted with a finely tuned form of telepathy that allowed him to "hack" into almost any mind.