Christie, Parker & Hale
Disk drive pulse detection method and circuit
 The combination of a rotating data storage disk and a pulse detector for generating an output pulse synchronized with clock pulses. The detector has a beginning of input pulse sensor for pulses derived from the disk, a timing circuit responsive to the sensing of the beginning of one of the input pulses for generating an output pulse of substantially constant pulse width and synchronized with clock pulses. A pulse presence sensor inhibits the timing circuit from generating another output pulse for any such detected input pulse, until after the sensed input pulse terminates. 
Western Digital Corporation
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Mehdi Takashi
Bathaee Asami