SUBMARINE SIGNAL COMPANY AND SUBMARINE SIGNAL CORPORATION v. HENRY HUGHES & SON, LTD.

(1931) 41 Ll L Rep 241

COURT OF APPEAL.

Before Lord Hanworth (Master of the Rolls), Lord Justice Lawrence and Lord Justice Romer.

Patent - Infringement - Echo sounding apparatus for use in ships-"Fessenden" patent-Claim for injunction and damages-Defence of invalidity and non-infringement - Meaning of "electric oscillator" - Doctrine of mechanical equivalents-Finding of learned Judge that defendants' sound emitter was simply a mechanical equivalent for the electric oscillator in plaintiffs' apparatus, which constituted an infringement -