A radiotelephone is any device that is used to send voice transmissions over radio waves. A wide variety of devices fall under this definition. Many radiotelephones can relay messages through traditional land phone lines, while others are used exclusively for mobile-to-mobile wireless transmissions. A number of modern devices such as cell phones are technically classified as radiotelephones.
The most basic kind of radiotelephone is a simple transceiver that sends voice signals to another station. The radios used by police cars are examples of standard radiotelephones. Ships, aircraft, and military units also commonly use radiotelephones for communication, since they often operate in situations where other voice transmission methods are not available.
In the United States, radiotelephone signals have been regulated by the Federal Communications Commission (FCC) since the 1930s. Under FCC regulations, a radiotelephone is different than a telegraph or Morse code transmitter because it is specifically intended to wirelessly transmit speech. Though technology has changed significantly since the early days of voice communication, the FCC continues to offer a radiotelephone operator license. This certification is required for anybody who uses high-powered ship or aircraft radios.
The technical definition of a radiotelephone extends beyond simple point-to-point transceivers, and also includes radios that can interface with the land phone system. In this arrangement, a base receiver is connected to a normal phone. Voice signals sent from a mobile radio are picked up by the base station and forwarded through the phone lines. A human operator may be used to connect calls, or an automated tone-controlled system can be utilized. These types of radiotelephone installations were fairly common before cell phones became prominent.
Cell phones are in fact radiotelephones, although they are rarely called by this name today. Each “cell” or area of phone coverage contains a radio station that is linked to the traditional phone grid. A handheld cell phone unit contains a short range radio transceiver. Early cell phone radiotelephone conversations were sent via a standard radio signal and could be picked up by any receiver on the proper frequency. Modern calls are encrypted to prevent eavesdropping.
Despite the popularity of cell phones, many people still use more simple radiotelephones for professional and hobby communication. Businesses often employ mobile voice radios to talk in areas that are outside of cell coverage, such as remote construction sites. Amateur radio experimenters use handheld and vehicle radiotelephones to connect with other enthusiasts, and have access to private radio repeaters that are similar to the mainstream cell phone networks.