A frequency-modulated magnetic Recorder

Limitations of tape recording of amplitude modulated signals are: 1. Inherent frequency response of magnetic recording systems is not flat, necessitating compensation networks. 2. D-C signals cannot be recorded with conventional recording heads and circuits. 3. A variation of about 1 DB (12 per cent) can be expected in the characteristics of the magnetic material used on the tape. These limitations are overcome by using the signal to be recorded to change the frequency of an oscillator, which is in turn recorded on the tape. This f-m signal can be played back - if desired at a lower speed (and hence lower frequency) - to a demodulator, which retranslates the f-m signal into an a-m signal for direct writing recorders.