Signal processing system

Claim 1

In an echoscope including in series: a transducer to receive echoes of an earlier transmitted non-electrical signal and to convert the received echoes into representative electrical signals; a time gain compensation amplifier to amplify said electrical signals in dependence upon the relative delay time between transmission of the original non-electrical signal and receipt of the echo; and compression means to limit the amplitude range of the signals received from the time gain compensation amplifier; the improvement wherein said compression means comprises: a plurality of amplitude limiting means connected in series to pass signals applied to the first such means while compressing the amplitudes of those applied signals which exceed a characteristic value for each such means, the electrical parameters of each amplitude limiting means being selected such that the characteristic applied signal amplitude values for the amplitude limiting means are successively smaller, an adder connected to produce an adder output signal being the sum of adjustable proportions of the output signals from at least the first and last of said series connected amplitude limiting means; and a switch for selectively producing a final output signal comprising either an output from said last amplitude limiting means or said adder output signal.