The telephone also was influenced by the digital age. At Bell Labs in 1948, around the same time the transistor was being invented, mathematician Dr. Claude Shannon published "A Mathematical Theory of Communication," which promoted the concept of communicating in binary code. Dr. Shannon's paper formed the basis of the entire digital communications revolution, from cell phones to the Internet.

It took 15 years for AT&T to act on Dr. Shannon's ideas. In November 1963, Ma Bell introduced Touchtone service, which enabled calls to be switched digitally and, later, enabled all manner of automated menus and functionality that eliminated the need for human operators. The new digital networks initiated the replacement of the rotary phone dial with push-button numerical keypads, even though the act of calling someone is still referred to as "dialing."

After Federal Superior Court Judge Harold H. Greene presided over the dismantling of AT&T in 1984, consumers were allowed to buy their own telephone instead of renting it from the phone company. The result was a wave of new designs and functions for the home phone by dozens of manufacturers that made Alexander Graham Bell's invention a true consumer electronics product more than 100 years after it had been invented.

In the mid-1990s, the concept of CallerID – the ability to see a name and phone number of the calling party on a small screen – gained popularity. This development occurred at about the same time that digital answering machines, able to record messages on a chip, began to replace decade-old tape-based units.

Americans were freed from their phones in the 1970s with the introduction of cordless models that used low-power, low frequency radio waves to transmit calls from the base to the handset and back again. But the real cordless breakthrough was the exploitation of higher bandwidth 900 MHz, 2.4 GHz and 5.8 GHz frequencies thanks to a World War II technology called spread spectrum, co-invented by one of Hollywood's most glamorous stars, Hedy Lamarr.

The Austrian-born Lamarr was married to an arms merchant and learned about radio-controlled weapons. After fleeing both her husband and Austria prior to the war, she became a movie star but remained interested in helping her adopted country defeat the Nazis. Together with orchestra leader George Antheil, Lamarr proposed a frequency-hopping radio-controlled torpedo system that would be impervious to Nazi radio jamming, applying for and receiving U.S. patent #2,292,387 for the idea. Lamarr and Antheil gave their patent to the Navy, but the technology was not exploited during the war.

In the late 1950s, Sylvania's Electronic Systems Division devised an electronic version of the frequency-hopping technology and applied it to the problem of securing military communications, later using it during the 1962 Cuban Missile Crisis. Lamarr and Antheil's patent expired in the late 1950s, but frequency-hopping, now called spread spectrum, remained a highly classified military technology. The most well known military usage of spread spectrum is the Global Positioning Satellite (GPS) system that now guides both military weaponry and consumers who have lost their way.

Consumer telephone makers also adopted spread spectrum technology, resulting in cordless phones with 10 times the range of previous cordless models and eliminating most interference and potential eavesdropping. But as much as the cordless phone freed consumers in their homes, they began to desire completely mobile wireless communications, phones they could take with them wherever they roamed on the planet.

CB Radios
In 1938, while still in high school, an 18-year-old amateur radio operator from Cleveland named Al Gross invented the walkie talkie.

During WWII, Gross worked for the Office of Strategic Services (OSS), the forerunner of the CIA, in developing a secret long-range wireless communications system for military intelligence use. After the war, the FCC based its creation of the Citizens Radio Service Frequency Band (1946) on Gross' wartime wireless work.

Gross, formed a company called Citizens Radio Corp. to produce two-way radios for personal use. Two years later, Gross' company was the first to receive FCC approval for making consumer radios using the new so-called "Citizens' Band" using shortband 226-27 MHz frequencies. Cartoonist Chester Gould was so taken with the idea that he asked Gross if he could borrow the idea, resulting in Dick Tracy's two-way wrist radio. Initially, CBs were used primarily by military, marine and emergency services. It took 25 years – for the gasoline shortage, a truckers' strike and a pop song called "Convoy" by C.W. McCall in the mid-1970s – to bring CB to the mass public's attention. It 114 became the biggest electronics fad of the decade.

In 1976, CB sales hovered around 11 million units, but after the FCC expanded the band to 40 channels and banned the sale of 23-channel units after Dec. 21, 1977, sales declined.

Today, CB still is popular, especially in the form of hand-held, battery-operated units for use in emergency situations. Person-to-person communication has been enhanced with the 1996 allocation of UHF-based family radio service (FRS) frequencies, 14 channels and 38 sub-channels, along with the more powerful 16-channel General Mobile Radio Service (GMRS), all operating within the 460-MHz band, which enables CB-style communication for users within one to five miles of each other, depending on local topography.

Pagers
People don't always need to talk to communicate. In 1921, the Detroit police department started alerting its officers simply by transmitting a signal that made a device "beep," which logically resulted in the new devices being dubbed "beepers."

But the first true pager would take nearly 40 years to be developed. In 1949, CD developer Al Gross patented the telephone pager. New York's Jewish Hospital started using Gross' pager system the following year. But the FCC didn't approve the system until 1958, and the first consumer paging systems didn't appear until the mid-1970s.

By the mid-1990s, text messages dictated to operators could be received, and in 1997, paging went two-way thanks to pagers with tiny keyboards and new two-way paging networks. In the late 1990s, pager companies such as Research-in-Motion (RIM) began introducing specialized email pagers, small devices with keyboards that enabled users to send and receive email. Pagers also got smaller; two companies, Seiko Communications and MTX – a partnership between Motorola Inc. and Timex Corp. – introduced watches that incorporated pagers.

But the business of text messaging would soon be passed to another, more expansive communications device: the cell phone.

Cell Phones
While CB radios and pagers provided some mobile communications solutions, what people really wanted was a completely mobile telephone.

Experiments with radio-telephones began as far back as the turn of the century, but most of these attempts required the transport of bulky radio transmitters or using long poles to tap into local overhead telephone wires.

The first practical mobile radio-telephone service, MTS (Mobile Telephone Service) was begun in 1946 in St. Louis. But this first system was more like a radio walkie-talkie – operators handled the calls and only one person at a time could talk.

The idea of permanent "cells" was first broached in 1947 by AT&T researcher D.H. Ring, the same year radio-telephone service was initiated between Boston and New York by AT&T. Automatic dialing – making the radio-telephone call without the use of an operator – began in 1948 in Indiana, but it would be 16 years before the innovation was adopted by the Bell system.

During the next 15 years, the transistor along with other technologies, and a steady increase in frequencies allotted to the new technology, continued to improve radio-telephone service.

In 1964, AT&T developed a second-generation cell phone system called Improved Mobile Telephone Service (IMTS), which had more of the hallmarks of a standard telephone but allowed only a limited number of subscribers and was used only in cars. In most metropolitan areas in which the service was available there was a long waiting list.

The idea of a mobile phone was popularized by Secret Agent 86, Maxwell Smart, who used a shoe phone on the 1960s TV spy spoof series, "Get Smart". But by the late 1960s, there were far more consumer requests for IMTS car telephones than there were channels available. The IMTS industry, known as the Land Mobile Radio Service, led by AT&T and Motorola, lobbied the FCC for additional bandwidth in the 806-960 MHz frequency band. However, local VHF television stations were using much of this band. In May 1970, after a fierce battle with the broadcasting industry, the FCC assigned the frequencies to the land mobile industry.

While the battle raged with broadcasters over the 806-960 MHz band, AT&T, Motorola and several other companies made various proposals on how to carve up and most effectively utilize the new frequency bands. In mid-1968, the FCC opened the so-called "cellular docket," Docket 18262, to address the reallocation of these new frequencies. On December 20, 1971, AT&T submitted a proposal to the FCC for the use of these frequencies for a new type of radio-telephone system that used an alternative to the usual one-transmitter/many receiver's radio transmission model.

Instead, a team from AT&T, led by Dr. Joel Engel and Richard Frenkiel, proposed carving up a metropolitan area into adjoining hexagonal "cells," each with its own low-power transmitter. As a user drives from one cell to another, the system would "handoff" the transmission from a transmitter in one cell to a new transmitter in the next cell. This "cellular" scheme allowed different users to use the same channels in different cells, so called frequency reuse, vastly expanding the number of possible channels available and number of users a system could support.

AT&T's revolutionary proposal, however, also suggested that Ma Bell gain a monopoly over the new frequencies. Motorola, the primary equipment supplier to the car phone market, made a counter proposal, illustrating that the frequencies could be used by more than just car phones and, therefore, a monopoly hold on the frequencies was unnecessary. Whether Motorola actually believed that there was a credible market for bulky radiophones outside the car was another matter.

In the fall of 1972, Motorola project manager Dr. Martin Cooper proposed a number of different communications systems using the new frequencies. In March and April 1973, Cooper and his team demonstrated several of these hand-built systems for Washington legislators, FCC commissioners and the press. One of these devices was a handheld radiotelephone system dubbed the DynaTAC (Dynamic Total Area Coverage), which used the 900 MHz bandwidth and a version of AT&T's cell scheme. While technically not a "cell phone" – the single base/handset DynaTAC system more closely resembled what would eventually become the cordless telephone – it was the first demonstration of a wireless portable telephone, the Rosetta Stone for what would become the cellular phone.

The suitability of the new frequencies beyond their use for car phones finally helped convince the FCC not to give AT&T a monopoly and to allow so-called "common carriers" to share the new spectrum. But it took until May 1981, after more than a decade of legal wrangling, for the FCC to finalize the rules and allocations for cellular spectrum.

Meanwhile, several experimental licenses were granted for testing the new cellular systems. AT&T developed the advanced mobile phone system (AMPS), the first regular U.S. cellular phone system using microwave transmissions, which began trials in 1977 in Chicago. After five years of tests, full commercial AMPS service was officially initiated on October 12, 1983 in Chicago. In its first year, there were a half million subscribers. By the end of the decade, there were two million.

But neither AT&T nor Motorola predicted the consumer desire for mobile phones; all the early cell phone companies believed the new technology would be used for emergency services, as land mobile car phones had been. But consumer demand soon far outstripped the supply of frequency bands and cell phone numbers, despite the fact that "portable" phones were barely that. These early cell phones were the size and weight of small bricks, required large and heavy batteries and often had to be carried in briefcases.

The analog systems could not contain the unexpected deluge of wireless customers. In 1990, the digital standard time division multiple access (TDMA) system was established and, when first introduced in 1992, tripled capacity and vastly improved sound quality.

In 1994, an alternative digital standard, code division multiple access (CDMA) technology was introduced by Qualcomm. In December of that year, the FCC began to auction off the 1900 MHz bands, so-called "PCS" (Personal Communications Service) bands, for digital cell phone use.

By 1996, thanks to single-chip digital signal processing (DSP) chips first unveiled in 1983 by Texas Instruments, cellular phones became pocket-sized and "wearable." Every major carrier was offering digital PCS, which allowed a raft of messaging and information services and features to be accessed in addition to voice calls.

Personal communications took to the skies in late 1998 when both satellite phones and satellite e-mail devices were introduced, the former from Iridium and Motorola, and Globalstar, and the latter from Magellan. Unfortunately, satellite phone service proved too costly for most consumers. Iridium ceased operation in March 2000 and the satellites for other proposed satellite phone providers were never launched. The military now is the primary user of heretofore consumer satellite phones.

In 1999, wireless phones converged with handheld personal computers, combining wireless phone service, Web access and personal digital assistant (PDA) capabilities in a single pocket-sized device. The first such device came from Qualcomm in 1999 with its pdQ 800, a cell phone with a built-in Palm Pilot. That same year, the Neopoint 1000, the first cell phone with wireless Web access, went on sale. In 2001, Samsung unveiled the SPH-i300, the first combined color Palm PDA cell phone.

In 2001, so-called "third generation" (3G) digital cell phones –actually more like 2G and 2.5G since data transmission speeds did not reach broadband levels – started to appear. True 3G EDGE (Enhanced Data GSM Environment) and Ev-DO (Evolution Data Only) broadband networks capable of providing data transmission speeds in excess of 384 kbps became available in most metropolitan areas in late 2004.

Speedier broadband networks powering these phones allow the transmission of pictures, video and digital music as well as voice, vastly speedier wireless Web access connections, and allowed the cell phone to be used as a wireless modem when attached to a laptop computer, a digital music player or even a TV. Several carriers began transmitting both live and packaged TV clips through cell phones in late 2004, and the first true MP3 phones with multi-gigabyte memory through which consumers could access and download tracks from cell carriers began to appear in mid-2005.

Once consumers signed with a carrier, they were stuck with that carrier if they wanted to keep their phone number, which limited consumer choice. In September 2003, the FCC enacted Local Number Portability, which allowed consumers to take their cell phone number with them when they switched carriers, or even transfer their home landline phone number to a cell phone.

Competition from a wide variety of local, regional and national cell carriers has driven the price-per-minute down to the point that the cost of using a cell phone rivals or surpasses that of a home phone. These economics, combined with a cell phone's portability, have prompted many consumers to forego their home phones and opt simply for a cell phone. As of early 2005, there are more than 180 million cell phone users in the U.S. alone.