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SUMMARY

This chapter briefly covered the historical development of magnetic recording principles and devices. The following is a summary of important points in the chapter.

The BEST MAGNETIC RECORDING is one that produces an output signal that is identical to the input signal. However, a step in the magnetic curve causes the output signal to be distorted.

In 1907, DC BIAS was added to the input signal to remove the distortion in the output signal. But the dc bias caused a weak output signal with a poor SNR. Around 1925, the NRL used AC BIAS to reproduce a stronger output signal and greatly improve the SNR.

To perform magnetic recording, you need (1) an INPUT SIGNAL, (2) a RECORDING MEDIUM, and (3) a MAGNETIC HEAD.

A RECORDING MEDIUM is any material that can become magnetized in varying amounts (such as magnetic tape and disks).

MAGNETIC HEADS are used to (1) record the signal onto the recording medium, (2) reproduce the signal from the recording medium, and (3) erase the signal from the recording medium.