December 31, 2011

History of Mobile Phone

Radio telephony, that is, the integration of radio transmission with tradional swiched telepohone network, was some what superficially examined in thsi period(Brooks 1976). However the new medium was generally chaneled into other areas. In addition to marine communications, the period saw the development of commercial broadcast radio. In Detroit in early 1920s, radio communication was used to coordinate the activities of police , taxis etc(Manning 1996;Farley 2003; Dobsen 2003)

The development of the transistor after second World War led to next significant development in mobile telephony, namely, the regular use of radio telephony for switched communications. From the late of 1800s, landline telephony had offered person to person communication via switched circuits. A dedicated circuit , or a “line”set up between two persons calling each other. The early determined who the calling party wished to reach and then connected the two with the use of a cable and a jack. These switches were progressively automated until thousands or evens millions of simultaneous conversations

The wide scale integration of radio based telepone devices with traditional switched telephony systems satrted in the late 1940s. A push to speak” switch on the handset opened and closed channel for for the caller . This controlled the pace conversation. In order to hear the response the person called, you would have to release the switched . Presumably, the conversation would include conventions such as “copy”,”over”, and roger”,in order to facilitate taking turns. Interestingly, the development of “push to talk” systems are reviving this one way form of interaction.

By the mid -1960s an improved system was develop. In this case there automatic channel assignment , direct dialing abd full diplex opperation. The system in a specific geographic are allowed for about a dozen simultaneous users. In 1976, There were 3700 customers on waiting list(Encyclopedia Britannica 2002). The mobile terminals them selver were ponderous this requiring batteries heavies than a car battery. Thus , mobile telephony at this point meant automobile based telephony.

The 1980s saw increasing interest in the development of various mobile telephony standards. I the US, these included the mutually incompatible Advanced Mobile Phone System (AMPS), Narrowband Advanced Mobile Phone System(NAMPS). Time –Division Multipme Access(TDMA) and the Code-Division Multiple Acces (CDMA). These system progressively allowed increasing capacity as mobile telephony became more popular.