Helical scan

Helical scan

Helical recording method. As the tape moves horizontally, the drum rotates and the heads in the drum create or write diagonal tracks with signals.
Media type	magnetic tape
Usage	recording high-frequency signals

Helical scan is a method of recording high-frequency signals on magnetic tape, used in open-reel video tape recorders, video cassette recorders, digital audio tape recorders, and some computer tape drives.

With this technique, magnetic tape heads (or head chips) are placed on a rotating head drum,^[1] which moves the chips at high speed (or angular velocity). The tape is wrapped tightly around the drum. The drum^[2] and/or the tape is tilted at an angle that allows the head chips to read the tape diagonally, and the linear speed of the tape is slower than the speed of the head chips, allowing signals to be transmitted. High frequency signals, such as video, are recorded. Due to geometry, helical scan allows for high head chip speeds, known as writing speeds, to be achieved in spite of the low linear speed of the tape. The high writing speed allows for high frequency signals to be recorded.^[3][4][5] The diagonal tracks read or written using this method are known as helical tracks.^[2]