How Does an Audio Cassette Work?

Tape Types

Cassette tapes are all fundamentally the same--they feature two spools of tape with a pattern of magnetically charged particles on it that can be manipulated to reproduce sounds. The four major types of types are simply called type I, II, III, and IV.

Type I tapes are composed of plastic tape with a magnetic ferric oxide coating--these tapes are often used for low range recording. Type II tapes use a ferrite or cobalt coating and work well with music. The abandoned Type III format uses a ferric oxide magnetic coating for recording. Type IV offers the wide range and best sound quality with an iron coating.

Playing

When you insert the tape into a player, the two spools of tape are mounted onto to rollers. Pressing "Play" on your cassette player, activates a motor that turns and moves the tape with a series of rollers called capstans and pinch rollers.

As the magnetically coated plastic tape passes below the lowered playing head, a current is created. The playing head contains an electrical coil that reacts with the organized magnetic particles of the tape to create electrical vibrations. The patterns from these pulses are converted into audio by the player and broadcast through an output such as a set of speakers or a pair of headphones.

Recording

When your insert your cassette into a tape player/recorder and press the record button, a magnetic head is engaged. The head receives audio signals from its source--the radio or another tape-- and the tape is queued along the magnetic head, it rearranges the magnetic particles on the audio tape to match the frequency of the source.

The magnetic particles are permanent fixtures of the tape's surface. Particles on a new tape are unorganized--the recording head arranges them. The sound source dictates their placement. Artifacts from the original sound produces varying amounts of pressure.

These pulses of pressure regulate the flow of electricity to the magnet--strengthening and weakening it. The fluctuations in the magnet's strength cause the tape's particles to cluster into groups that mimic the pulses. When the playing head is engaged, the clusters of particles react with the head to create an electrical current. The current is sent the opposite way of the recording head.

The pulses of the playing head are an exact copy of the original current that was passed through the recording head to arrange the particles. The current is sent to the speakers. The speakers receive the varying pules and interprets them as unique vibrations of the original sound.