Signal detection apparatus

Claim 1

In a system for detecting, in the presence of noise signals, noiselike signals from a transducer, a receiver comprising: a. first amplifying means, responsive to noise signals and to noiselike signals from the transducer, for producing signals varying in accordance with both such signals; b. multiplexing means for dividing the signals out of the first amplifying means into a first signal path and a second signal path, the first such path including filter means for passing the noiselike signals and the second such path including filter means for rejecting the noiselike signals and passing the noise signals, the second Such path including second amplifying means; c. demodulating means, responsive to the signals out of the first and the second signal path, for producing first and second unipolar signals varying, respectively, as the signals out of the first and the second filter means; d. integrating means, responsive to the first and the second unipolar signals, for producing signals varying, respectively, as the root mean square value of such unipolar signals; e. feedback means, responsive to the signals out of the integrating means in the second signal path, for controlling the gain of the second amplifying means; and f. a threshold circuit, responsive to the signals out of the integrating means, for producing output signals when the root mean square value of the first unipolar signal exceeds the root mean square value of the second unipolar signal by a predetermined amount.