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Radio Corp. v. Dubilier Condenser Corp.

March 18, 1932

RADIO CORPORATION OF AMERICA
v.
DUBILIER CONDENSER CORPORATION ET AL.



Appeal from the District Court of the United States for the District of Delaware; Hugh M. Morris, Judge.

Author: Woolley

Before WOOLLEY and DAVIS, Circuit Judges, and JOHNSON, District Judge.

WOOLLEY, Circuit Judge.

This appeal is from a decree of the District Court holding claims 3 and 14 of Lowell and Dunmore Patent No. 1,455,141 valid and infringed by the defendant's apparatus of the types known as Radiola 17 and Radiola 18. 34 F.2d 450. The patent, entitled "Radio Receiving Apparatus," discloses and claims means for the use of alternating current from the standard residence lighting power in lieu of direct current from batteries in radio receiving sets of the three-section type consisting of radio frequency amplifiers, a detector and audio frequency amplifiers. The invention is directed particularly to the elimination of hum occurring in the vacuum tubes when they are heated by unrectified alternating current.

In order to view this invention in its proper setting it will be necessary briefly to advert to the art as it stood in March, 1922, when the application was filed.

Wireless transmission of sound through ether effected by electrically created waves had long been known and practiced. Though in itself a great invention, the first real impulses toward its amazing development and general public use were given by the Fleming valve and the DeForest tube, the latter patented in 1908. Even with these capital inventions the development of radio lagged until about 1912 or 1913 when it became rather actively employed sometimes by telegraph and telephone companies but particularly by governments in the transaction of their business. It was also used by amateurs, chiefly youths, who, rigging up receiving sets according to their own notions, delighted in reaching through the air for distant messages and in delving into the mysteries of the young art. More important however, inventors rushed into this new field and crowded it with almost innumerable inventions, some of which were good and most of which were of no account. Still, radio as a practical instrumentality was for years restricted to professional and amateur uses. It was not until March 4, 1921, when the Westinghouse Company broadcast the inaugural ceremonies at Washington, that the first general broadcast by radio, to be picked up by any one playing with the art, was made, and it was not until fall of the same year that the first broadcasting station -- KDKA -- affording entertainment was established by the Westinghouse Company at Pittsburgh. Other broadcasting stations quickly followed. Immediately there arose a public demand for receiving sets, and immediately commercial sets were placed on the market by zealous manufacturers. Of various types of sets the one most favorably received, patterned after sets already in specialized uses, was the three-section type consisting of vacuum tubes and appropriate electric circuits of which we shall presently speak at greater length. These circuits were supplied with electrical energy by direct current from storage and dry cell batteries which became known according to their uses as "A," "B" and "C" batteries. When in constant home use, they soon became exhausted and had to be replaced. That involved expense.

Lowell and Dunmore thought this expense could be reduced substantially by using common house-lighting current. It was cheaper than current from batteries, but to employ it as a source of electrical energy they were confronted by two obstinate facts: One, house current is alternating current of about 110 volts and has a frequency of about 60 cycles a second; the other, these rapid and continued reversals of direction produce in a sound output receiving set a distortion of the modulation and a strong hum that make the reception unsatisfactory. Believing they had overcome these difficulties, Lowell and Dunmore invented the apparatus of the patent in suit, operated by home-alternating current instead of by direct battery current, and disclosed its elements and their functions by many claims. Claim 3 is typical. This claim, with elements which we have identified by letters for further consideration, reads as follows:

"In an apparatus for the reception of radio signals the combination (a) of a source of signal energy, (b) means for amplifying said signal energy at radio frequencies, (c) means for rectifying said energy, (d) means for amplifying said energy at audio frequencies, (e) a source of alternating current for supplying power to said amplifying means and (f) separate means connected to each of said amplifying and rectifying means for eliminating the hum of said alternating current in said apparatus."

Though the claim is for a combination, it will be necessary to look at each of the several means or elements of the invention, reference being made to the exhaustive opinion of the learned trial judge for a better understanding of their characteristics.

(a) "A source of signal energy." This is the electrically created waves sent through the ether by appropriate apparatus at a broadcasting station.

(b) "Means for amplifying said signal energy at radio frequencies." The waves that are picked up by the aerial are feeble and are of such high frequencies that they are inaudible. Their strength is raised and their frequencies lowered as the waves pass through a three-section receiver on to the loud speaker. The first section, being the "means" under consideration, contains one or more vacuum tubes ordinarily of the three electrode type. The tubes in this section amplify or raise the strength of the waves. That being their function, they became known as radio frequency amplifiers.

Still the waves, though stronger, are of such high frequencies -- radio frequencies -- that they are incapable of producing sound audible to the human ear. To make the waves with their hidden message audible and therefore useful, the second section comes into play. This is:

(c) "Means for rectifying said energy," and is a device, either a crystal or a tube, known as a "detector," which rectifies inaudible waves of radio frequencies and converts them into waves of such low frequencies that they come within the range of frequencies which are audible to the ear. They are then known as waves of audio frequencies. Though now audible, they are still rather feeble or not as pronounced as desired in a head telephone or loud speaker. Therefore the inventors provided.

(d) "Means for amplifying said energy at audio frequencies." Here the third section of the receiving set, consisting of one or more vacuum tubes, performs the final function, which is to amplify the waves, now of audio frequencies, to the desired volume, whence they ...


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