What Are Erase Heads?
Recording analog signals on tape was never a perfect process, largely due to limitations of the tape itself. It did, however, fill an important gap between earlier recording mediums and the digital age. Unlike digital recording, which codes an electric signal into a series of pulses, analog recording actually reproduces a signal wave on a magnetic tape for later reproduction. This capturing of a wave is done through electromagnetic transducer called tape heads.
Identification
The erase head is the mini transducer in the tape recorder that randomizes the magnetization of the tape. The tape itself contains an emulsion of magnetic oxide particles that can be arranged to encode an electronic signal. By scattering or randomizing the particles on the tape, anything recorded on it is effectively erased. When recording, the tape first passes through the erase head, cleaning it before moving to the record head.
Types
Any recording device that uses a tape will have an erase head, a record head, and a playback head, each serving a vital function in the overall performance of the product. In reality, the erase head and record head operate very similarly, with the difference being that the record head encodes a standard bias and the wave of the incoming signal, arranging the tape emulsion in a way that can be reproduced by the playback head. The tape heads of audio equipment are fixed with tape simply passing through them, but in video recording the heads rotate, producing a helical scan.
Features
The most primitive type of erase head is simply a magnet, which does the job of rearranging the oxide particles of the tape to conform to its magnetic field, effectively erasing any other signal transcribed upon it. Of course, a fixed magnet can't be shut off, so recorders employing this type of erasure generate a large amount of static on the tape. More advanced erase heads employ coiled transducer designs resembling the record heads and generate a high frequency, high amplitude wave of alternating current to wipe the tape clean.
Considerations
The gap in a record head through which the tape passes is crucial for the fidelity of the transcription applied to it. A very narrow opening, keeping the tape close to the transducer, allows for higher frequency recording and a stronger signal. Because these features are not crucial in simply erasing the tape, the gap in the erase head is usually much wider.
Significance
The erase head is allows audio tape to be recorded and rerecorded repeatedly. This gives the tape recorder a certain efficiency and convenience that made it useful in answering machines during the 1980s and early 90s before digital recording became the norm. The same was true in security cameras that periodically recorded over the same tape unless it was needed for further inspection, and data storage before the age of floppy discs and CDs.
Tags: erase head, record head, digital recording, erase head record, head record, head record head, oxide particles