Today in History – April 3, 1973 – Martin Cooper of Motorola invented the cell phone and provides a public demonstration. He made the call to his rival, Joel Engel, Bell Labs head of research.

Motorola and AT&T Bell Labs were competing to develop cellular communications in the sixties and early seventies. Although AT&T’s Bell Laboratories introduced cellular communications in 1947, Martin Cooper was the first to incorporate the technology into portable devices. His experiment began with a base station in New York and the first working prototype of a cellular telephone, the Motorola Dyna-Tac. After some initial testing in Washington for the F.C.C., the cellular phone technology was shown to the public in New York. The Dyna-Tac weighed roughly 2.5 pounds, included 30 circuit boards and required 10 hours to charge for 35 minutes of talking time.

The technology of modern cell phones started with the creation of hexagonal cells for mobile phones by D.H. Ring from Bell Labs in 1947, later on another engineer from Bell Labs conceived of cell towers that would transmit and receive signals in three directions instead of normal bi directional antennas. By 1967, mobile phone technology was available; however, the user had to stay within one cell area. In 1970, Amos Edward Joel developed the call handoff system to facilitate continuity of a phone call from one area to another without dropping the phone call. In 1971, AT&T submitted a request to the FCC for cellular service. It took more than 10 years for an approval and in 1982; the FCC allocated the frequencies of 824-894 MHZ Band to Advanced Mobile Phone Service (AMPS). From 1982 to 1990, AMPS was an analog service, Digital AMPS came online as of 1990.

The first mobile phones were installed in vehicles due to the large battery requirements. The MTA (Mobile Telephone System A) developed by Eriksson was available in Sweden in 1950’s. Unfortunately, it weighed over 80 pounds, later versions however weighed around 20 pounds, still making it ineffective for mobility. In 1983, Motorola unveiled the Motorola DynaTAC 8000X, the first truly portable cellular phone. It weighed 28 ounces and was known as the Brick for its shape.

From 1983 to the end of the 1980’s cell phones grew in popularity, although most were made for permanent installation in the car. There were also briefcase models that held large batteries necessary to make calls. Cellular phones from the early 1990’s are considered second generation (2G) and they were able to work on mobile phone systems such as GSM, IS-136 (TDMA) and IS-95 (CDMA). Digital mobile phone networks were in use in the United States in 1990 and in Europe by 1991. 2G mobile phones use digital circuit switched transmissions, which enable quicker network signaling, fewer dropped calls and increased quality.

The Third Generation (3G) cellular phone is the latest technology. While 3G came only a few years after 2G, mainly due to many innovations in technology and services, standards for 3G are usually different depending on the network. Smartphones utilize the advanced capabilities of 2G and 3G beyond typical mobile phones, often with PC-like functionality. Mobile phones are quickly becoming the dominant computer and telephony platform in most of the developing world. Cell phones are pervasive in North America, Europe and Asia and sales statistics are often shown in predictions for future growth, as if 1 billion is not enough.

For more information, see the Engineering Pathway’s resources on the cell phones and telecommunications. Additional curricular materials can be found on the Computer Engineering Education and the Electrical Engineering Education Community site.