Phone bugs are among the most popular of devices for surveillance. This is because there is something that humans enjoy about listening in on conversations and learning things that others may not want them to learn. For those who aspire to involve themselves in professional surveillance, and even for those who just participate in surveillance as a hobby, knowing the basics of phone bugs is valuable information.

Phone bugs are interesting because they are versatile. There are different types of these listening devices, and it is even possible to combine two or more different bugs into one bug that can act as its own backup device. These hybrid phone bugs are constructed from one of four different eavesdropping techniques: radio frequency (RF), ultrasonic, optical, and acoustic.

RF phone bugs are the most popular of covert listening devices. This is because they are inexpensive and they are difficult to trace. Even if the bug is discovered, chances are that it will not be traced to you. Radio waves are transmitted from the bug