rst produced and observed it in 1887. All mod- ern communication depends on manipulating and controlling signals within the electromagnetic spectrum. The electromagnetic spectrum ranges from extremely low-frequency radio waves of 30Hz, with wavelengths nearly double the earth's diameter, to high- frequency cosmic rays of more than 10 million trillion Hz, with wavelengths smaller than the nucleus of an atom. The electromagnetic spectrum is depicted as a logarith- mic progression: The scale increases by multiples of 10, so the higher regions encompass a greater span of frequencies than do the lower regions. Although the electromagnetic spectrum represents an enormous range of fre- quencies, not all the frequencies are suitable for human communications. At the very low end of the spectrum are signals that are transmitted over 30Hz (i.e., at 30 cycles per second). One of the most important benefits of a very low frequency is that it travels much farther than a high frequency before it loses power (i.e., before it attenuates). So a 30Hz signal can travel halfway around the world before it Chapter 1 Telecommunications Technology Fundamentals requires some form of amplification. For example, one defense agency uses 30Hz to communicate with its submarines by using telemetry (e.g., a message that says "We're still here. We're still here" is sent, and the subs know that if they don't get that message, they'd better see what's going on). At the high end of the electromagnetic spectrum, signals travel over a band of 10 million trillion Hz (i.e., 10 HH). This end of the spectrum has phenomenal bandwidth, but it has its own set of problems. The waveforms are so miniscule that they're highly distorted by any type of interference, particularly from environmental sources such as precipitation. In addition, the faster the bit rate, the more power consumed. For example, submarine fiber-optic cables require approximately 20,000 watts of power on each end to work. Furthermore, higher-frequency waveforms such as x-rays, gamma rays, an