Phones are as integral to modern life as it gets, and richly deserving of a careful look by all. The first public telephone call placed on a portable cellular phone was made by Martin Cooper on April 3, 1973. Smartphones use a “full-duplex” radio, meaning that the smartphone uses one channel for sending and a different channel for receiving, a decided advantage given that two or more people can then talk or listen at the same time. In the case of smartphones, a more complicated carrier modulation scheme is required. In the context of smartphones, channel “bandwidth” is the range of frequencies that the transmitted-received signal uses. A cellular service provider is given a certain number of channels to distribute among its available cells. The usefulness of a smartphone begins and ends with the radio, because the radio transceiver must seamlessly interface between the phone and the electromagnetic world for signal reception and transmission.