A public address system (PA system) is an electronic sound amplification and distribution system with a microphone, amplifier and loudspeakers, used to allow a person to address a large public, for example for announcements of movements at large and noisy air and rail terminals.

The term is also used for systems which may additionally have a mixing console, and amplifiers and loudspeakers suitable for music as well as speech, used to reinforce a sound source, e.g., recorded music or a person giving a speech, and distributing the sound throughout a venue or building.

Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with many speakers are widely used to make announcements in public, institutional and commercial buildings and locations. Intercom systems, installed in many buildings, have microphones in many rooms allowing the occupants to respond to announcements.

Sound reinforcement systems and PA systems may use some similar components, but with differing application, although the distinction between the two is not clear-cut. Sound reinforcement systems are for live music or performance, whereas PA systems are primarily for reproduction of speech. In Britain any PA system is sometimes colloquially referred to as a Tannoy, after the company of that name now owned by TC Electronic Group, which supplied a great many of the PA systems used in the past.

DJ Micro (born Michael Marsicano) is an American trance DJ and producer.

DJ Micro began on the East Coast, where in 1991 he helped form the Caffeine Records collective in Deer Park, NY. Caffeine began as a weekly club night, and started building a brand. Micro spun at many of Caffeine's parties, specializing in acid breaks. In 1994 he joined with Vicious Vic under the moniker Progression. They obtained massive popularity in the international dance scene after the release of their debut single Reach Further. They were soon commissioned to remix artists such as Paradise 3001, Joe T. Vanelli, Masters at Work, and even the X Files theme.

He recorded two mix albums for Roadrunner in the late '90s, Coast to Coast (1997) and Caffeine: The Natural Stimulant (1998). He later hooked up with Moonshine in 1998. Micro's first release for Moonshine, Micro-Tech Mix (1998), would be followed by a large succession of mix albums, usually one released annually.

DJ Micro aggressively toured the country recording mix albums for Moonshine Music to boost his popularity. Micro slightly changed his style with each album and moved toward trance while maintaining his breakbeat roots. By the end of the '90s, he had become one of the most popular DJs on the East Coast, considered in the same class of superstar DJs as Frankie Bones and Scott Henry^{[citation needed]}. Like them, Micro toured often, particularly on the East Coast.