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Welcome to absolutely free HD Porn in real hight quality with teen amateurs and mature whores, group orgy on sex parties, naughty american babes and indian homemade videos from XNXX, Worldsex, Xhamster, Xvideos, Beeg and other great HD Porn tubes.HD Fuck porn delivers free sex movies and free porn videos for 3 years and we made a new site for your comfort.The 201A and 201B Data-Phones were synchronous modems using two-bit-per-baud phase-shift keying (PSK).
By contrast, the original ITU V.22 standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) using phase-shift keying.
News wire services in the 1920s used multiplex devices that satisfied the definition of a modem.
-designed tests for electronically coupling a device to the phone lines.
This opened the door to direct-connect modems that plugged directly into the phone line rather than via a handset.
However, the modem function was incidental to the multiplexing function, so they are not commonly included in the history of modems.
Modems grew out of the need to connect teleprinters over ordinary phone lines instead of the more expensive leased lines which had previously been used for current loop–based teleprinters and automated telegraphs.An even lower-cost option was the Pennywhistle modem, designed to be built using parts from electronics scrap and surplus stores.In December 1972, Vadic introduced the VA3400, notable for full-duplex operation at 1,200 bit/s over the phone network.Like the 103A, it used different frequency bands for transmit and receive.In November 1976, AT&T introduced the 212A modem to compete with Vadic.Frequency-shift keying was used, with the call originator transmitting at 1,070 or 1,270 Hz and the answering modem transmitting at 2,025 or 2,225 Hz.The readily available 103A2 gave an important boost to the use of remote low-speed terminals such as the Teletype Model 33 ASR and KSR, and the IBM 2741.Modems are generally classified by the maximum amount of data they can send in a given unit of time, usually expressed in bits per second (symbol bit(s), sometimes abbreviated "bps"), or bytes per second (symbol B(s)).Modems can also be classified by their symbol rate, measured in baud.SAGE modems were described by AT&T's Bell Labs as conforming to their newly published Bell 101 dataset standard.While they ran on dedicated telephone lines, the devices at each end were no different from commercial acoustically coupled Bell 101, 110 baud modems.