| 摘要 |
<p>This invention relates to a system for audibly recognizing a received signal aurally unclassifiable because of its improper time duration and/or the frequency band occupied thereby. The received signal may be a carrier wave, modulated in amplitude and phase in accordance with the amplitude and phase of a signal to be recognized. In such case, the system includes modulator means for deriving quadrature base-band signal components. The system also includes a signal-storage device, such as a signal recorder movable at one speed during storage of a received signal thereon and at a different speed during retrieval of the signal therefrom, and means for storing the quadrature signal components in the storage device as received. Associated with the storage device is means for retrieving the signal components from the device at a time-rate differing from the storing rate and means for deriving from the stored signal components a signal representative of the instantaneous frequency of the retrieved signal. The system further includes means for developing a control signal varying in magnitude in accordance with the instanteous frequency of the retrieved signal and an adjustable-frequency audible-tone generator responsive to the control signal, which may be in the form of a voltage-responsive variable-frequency oscillator which has an output circuit effective to supply an audible signal representative of the received signal. Optionally, the system may further include means for deriving from the quadrature signal components a second control signal representative of the amplitude of the retrieved signal and means responsive to the second control signal for varying the amplitude of the audibletone output of the generator.</p> |
