Orison Swett Marden say...

Keberhasilan tidak diukur dengan apa yang telah anda raih, namun kegagalan yang telah anda hadapi, dan keberanian yang membuat anda tetap berjuang melawan rintangan yang datang bertubi-tubi.

Orison Swett Marden


Terkadang kita melupakan satu hal dalam hidup, yakni bagaimana anda hidup.

Setiap orang ditakdirkan berbeda, dengan kelebihan dan kekurangannya masing-masing, dan dengan kekuatannya masing-masing. Ketika anda lemah, anda menghadapi kekurangan anda, dan anda kalah. Banyak orang yang mengalaminya, namun hanya sedikit yang menyadarinya. kekalahan bukan sesuatu yang harus ditakuti dan dihindari, tapi justru dihadapi. Orang tak akan bisa melangkahi aral melintang kalau ia terus menjauhinya, bukan?

Orang yang terus menerus mengalami kekalahan bukan orang yang lemah dan bodoh, melainkan orang yang sangat kuat yang sedang mencari cara untuk menguasai dirinya, bagaimana ia harus bangkit. Saking kuatnya, ia tak pernah berhenti mencoba dan terus berjuang dengan segenap tenaga dan keberaniannya untuk mendapatkan apa yang seharusnya ia dapatkan.

Maka berjuanglah...

Nurul Asri Mulyani
Arcadia member
X2
SMAN 2 Ciamis

Wisdom of the Day

Urusan kita dalam kehidupan ini bukanlah untuk mendahului orang lain, tetapi untuk melampaui diri kita sendiri untuk memecahkan rekor kita sendiri, dan untuk melampaui hari keparin dengan hari ini.

Stuart B. Johnson

Modem

Modem (from modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio.

The most familiar example is a voiceband modem that turns the digital 1s and 0s of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone Systems (POTS), and once received on the other side, converts those 1s and 0s back into a form used by a USB, Ethernet, serial, or network connection. Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps". They can also be classified by Baud, the number of times the modem changes its signal state per second.

Baud is not the modem's speed in bit/s, but in symbols/s. The baud rate varies, depending on the modulation technique used. Original Bell 103 modems used a modulation technique that saw a change in state 300 times per second. They transmitted 1 bit for every baud, and so a 300 bit/s modem was also a 300-baud modem. However, casual computerists confused the two. A 300 bit/s modem is the only modem whose bit rate matches the baud rate. A 2400 bit/s modem changes state 600 times per second, but due to the fact that it transmits 4 bits for each baud, 2400 bits are transmitted by 600 baud, or changes in states.

Faster modems are used by Internet users every day, notably cable modems and ADSL modems. In telecommunications, "wide band radio modems" transmit repeating frames of data at very high data rates over microwave radio links. Narrow band radio modem is used for low data rate up to 19.2k mainly for private radio networks. Some microwave modems transmit more than a hundred million bits per second. Optical modems transmit data over optical fibers. Most intercontinental data links now use optical modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x109) bits per second. One kilobit per second (kbit/s or kb/s or kbps) as used in this article means 1000 bits per second and not 1024 bits per second. For example, a 56k modem can transfer data at up to 56,000 bits (7kB) per second over the phone line.

History

Modems grew out of teletype machines, which in turn grew out of automated telegraphs.

News wire services in 1920s used multiplex equipment that met the definition, but the modem function was incidental to the multiplexing function, so they are not commonly included in the history of modems. George Stibitz connected a New Hampshire teletype to a computer in New York City by phone lines in 1940. Modems in the United States were part of the SAGE air-defense system in the 1950s, connecting terminals at various airbases, radar sites, and command-and-control centers to the SAGE director centers scattered around the U.S. and Canada. SAGE ran on dedicated communications lines, but the devices at each end were otherwise similar in concept to today's modems.

A few years later, a chance meeting between the CEO of American Airlines and a regional manager of IBM led to development of a "mini-SAGE" as an automated airline ticketing system. The terminals were at ticketing offices, tied to a central computer that managed availability and scheduling. The system, known as SABRE, is the ancestor of today's Sabre system.

AT&T monopoly in the United States

For many years, AT&T maintained a monopoly in the United States on the use of its phone lines, allowing only AT&T-supplied devices to be attached to its network. For the growing group of computer users, AT&T introduced two digital sub-sets in 1958. One is the wideband device shown in the picture to the right. The other was a low-speed modem, which ran at 200 baud.

In the summer of 1960, the name Data-Phone was introduced to replace the earlier term digital subset. The 202 Data-Phone was a half-duplex asynchronous service that was marketed extensively in late 1960. In 1962, the 201A and 201B Data-Phones were introduced. They were synchronous modems using two-bit-per-baud phase-shift keying (PSK). The 201A operated half-duplex at 2000 bit/s over normal phone lines, while the 201B provided full duplex 2400 bit/s service on four-wire leased lines, the send and receive channels running on their own set of two wires each.

The famous 103A was also introduced in 1962. It provided full-duplex service at up to 300 baud over normal phone lines. Frequency-shift keying (FSK) was used with the call originator transmitting at 1070 or 1270 Hz and the answering modem transmitting at 2025 or 2225 Hz. The readily available 103A2 gave an important boost to the use of remote low-speed terminals such as the KSR33, the ASR33, and the IBM 2741. AT&T reduced modem costs by introducing the originate-only 113D and the answer-only 113B/C modems.

The Carterfone decision

Before 1968, AT&T maintained a monopoly on what devices could be electrically connected to its phone lines. This led to a market for 103A-compatible modems that were mechanically connected to the phone, through the handset, known as acoustically coupled modems. Particularly common models from the 1970s were the Novation CAT (shown in the image) and the Anderson-Jacobson, spun off from an in-house project at the Lawrence Livermore National Laboratory.

Hush-a-Phone v. FCC was a seminal ruling in United States telecommunications law decided by the DC Circuit Court of Appeals on November 8, 1956. The District Court found that it was within the FCC's authority to regulate the terms of use of AT&T's equipment. Subsequently, the FCC examiner found that as long as the device was not physically attached it would not threaten to degenerate the system. Later, in the Carterfone decision, the FCC passed a rule setting stringent AT&T-designed tests for electronically coupling a device to the phone lines. AT&T made these tests complex and expensive, so acoustically coupled modems remained common into the early 1980s.

In December 1972, Vadic introduced the VA3400. This device was remarkable because it provided full duplex operation at 1200 bit/s over the dial network, using methods similar to those of the 103A in that it used different frequency bands for transmit and receive. In November 1976, AT&T introduced the 212A modem to compete with Vadic. It was similar in design to Vadic's model, but used the lower frequency set for transmission. It was also possible to use the 212A with a 103A modem at 300 bit/s. According to Vadic, the change in frequency assignments made the 212 intentionally incompatible with acoustic coupling, thereby locking out many potential modem manufacturers. In 1977, Vadic responded with the VA3467 triple modem, an answer-only modem sold to computer center operators that supported Vadic's 1200-bit/s mode, AT&T's 212A mode, and 103A operation.

The Smartmodem and the rise of BBSes

The next major advance in modems was the Smartmodem, introduced in 1981 by Hayes Communications. The Smartmodem was an otherwise standard 103A 300-bit/s modem, but was attached to a small controller that let the computer send commands to it and enable it to operate the phone line. The command set included instructions for picking up and hanging up the phone, dialing numbers, and answering calls. The basic Hayes command set remains the basis for computer control of most modern modems.

Prior to the Hayes Smartmodem, modems almost universally required a two-step process to activate a connection: first, the user had to manually dial the remote number on a standard phone handset, and then secondly, plug the handset into an acoustic coupler. Hardware add-ons, known simply as dialers, were used in special circumstances, and generally operated by emulating someone dialing a handset.

With the Smartmodem, the computer could dial the phone directly by sending the modem a command, thus eliminating the need for an associated phone for dialing and the need for an acoustic coupler. The Smartmodem instead plugged directly into the phone line. This greatly simplified setup and operation. Terminal programs that maintained lists of phone numbers and sent the dialing commands became common.

The Smartmodem and its clones also aided the spread of bulletin board systems (BBSs). Modems had previously been typically either the call-only, acoustically coupled models used on the client side, or the much more expensive, answer-only models used on the server side. The Smartmodem could operate in either mode depending on the commands sent from the computer. There was now a low-cost server-side modem on the market, and the BBSs flourished.

Softmodem (dumb modem)

Apple's GeoPort modems from the second half of the 1990s were similar. Although a clever idea in theory, enabling the creation of more-powerful telephony applications, in practice the only programs created were simple answering-machine and fax software, hardly more advanced than their physical-world counterparts, and certainly more error-prone and cumbersome. The software was finicky and ate up significant processor time, and no longer functions in current operating system versions.

Almost all modern modems also do double-duty as a fax machine as well. Digital faxes, introduced in the 1980s, are simply a particular image format sent over a high-speed (commonly 14.4 kbit/s) modem. Software running on the host computer can convert any image into fax-format, which can then be sent using the modem. Such software was at one time an add-on, but since has become largely universal.

A Winmodem or Softmodem is a stripped-down modem that replaces tasks traditionally handled in hardware with software. In this case the modem is a simple digital signal processor designed to create sounds, or voltage variations, on the telephone line. Softmodems are cheaper than traditional modems, since they have fewer hardware components. One downside is that the software generating the modem tones is not simple, and the performance of the computer as a whole often suffers when it is being used. For online gaming this can be a real concern. Another problem is lack of portability such that other OSes (such as Linux) may not have an equivalent driver to operate the modem. A Winmodem might not work with a later version of Microsoft Windows, if its driver turns out to be incompatible with that later version of the operating system.

Source: en.wikipedia.org

Internet Service Provider

An Internet service provider (ISP, also called Internet access provider or IAP) is a company that offers its customers access to the Internet. The ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol datagrams, such as dial-up, DSL, cable modem or dedicated high-speed interconnects.

ISPs may provide Internet e-mail accounts to users which allow them to communicate with one another by sending and receiving electronic messages through their ISPs' servers. (As part of their e-mail service, ISPs usually offer the user an e-mail client software package, developed either internally or through an outside contract arrangement.) ISPs may provide other services such as remotely storing data files on behalf of their customers, as well as other services unique to each particular ISP.

End-User-to-ISP Connection

ISPs employ a range of technologies to enable consumers to connect to their network.

For home users and small businesses, the most popular options include dial-up, DSL (typically Asymmetric Digital Subscriber Line, ADSL), broadband wireless, cable modem, fiber to the premises (FTTH), and Integrated Services Digital Network (ISDN) (typically basic rate interface).

For customers with more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and synchronous optical networking (SONET) are more likely to be used.

Typical home user connection

• Dial Up
• DSL
• Broadband wireless access
• Cable Internet
• FTTH
• ISDN
• WiFi

Typical business type connection

• DSL
• SHDSL
• Ethernet technologies

Locality

When using a dial-up or ISDN connection method, the ISP cannot determine the caller's physical location to more detail than using the number transmitted using an appropriate form of Caller ID; it is entirely possible to e.g. connect to an ISP located in Mexico from the USA. Other means of connection such as cable or DSL require a fixed registered connection node, usually associated at the ISP with a physical address.

ISP Interconnection

Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. An upstream ISP usually has a larger network than the contracting ISP and/or is able to provide the contracting ISP with access to parts of the Internet the contracting ISP by itself has no access to.

In the simplest case, a single connection is established to an upstream ISP and is used to transmit data to or from areas of the Internet beyond the home network; this mode of interconnection is often cascaded multiple times until reaching a Tier 1 carrier. In reality, the situation is often more complex. ISPs with more than one point of presence (PoP) may have separate connections to an upstream ISP at multiple PoPs, or they may be customers of multiple upstream ISPs and may have connections to each one of them at one or more point of presence.

Source: en.wikipedia.org

Wise Word for Friendship

I can trust my friends. there people force me to examine, encourage me to grow. -Cher-

A good friend can tell you what is the matter with you in a minute. he may not seem such a good friend after telling. -Arthur Brisbane, The Book of Today-

Your friend is the man who knows all about you and still like you. -Albert Hubart-

For a shield from the storm, for a friend, for a love to keep me save and warm...
I turn to you. For the strength to be strong, for the will to carry on...
Des everything you do, foe everything that's true, i turn to you. -Christina Aguilera, I turn to You-

To be depressed is to be lonely; to have a friend is to be happy. -Guido-

In a friend you find a second self. -Lisabelle Norton-

Friends may come and go, but enemies accumulate. -Thomas Jones-

Friends have all things in common. -Plato-

Sometimes you pick your friend, sometimes they pick you. -Steve Klaka-

One loyal friend is worth ten thousand relaties. -Euripides, Greek Playwrite-