Some surveillance listening devices are parabolic microphones, parabolic dishes and sound amplifiers. Audio bugs, body wires and spy phones are some other surveillance listening devices.
The parabolic microphone is a collapsible, 20-inch, six-panel dish utilized for long-range listening to a maximum of 300 yards. Its equalizer allows the user to adjust the microphone to specific sound frequencies. The parabolic dish is an extremely lightweight 12-inch dish used for medium-range listening. It is a directional microphone and amplifies sound to up to 40 decibels. It doesn't amplify high-decibel sounds thereby making it safe to use. The sound amplifier also amplifies sound but is meant mainly for personal use.