Kellogg Switchboard & Supply Co. v. Dean Electric Co.

• Citation: 182 F. 991
• Decision Date: 08 February 1910
• Docket Number: 1,913.
• Parties: KELLOGG SWITCHBOARD & SUPPLY CO. v. DEAN ELECTRIC CO. et al.
• Court: United States Courts of Appeals. United States Court of Appeals (6th Circuit)

182 F. 991

KELLOGG SWITCHBOARD & SUPPLY CO. v. DEAN ELECTRIC CO. et al.

No. 1,913.

United States Court of Appeals, Sixth Circuit.

February 8, 1910

Rehearing Denied June 18, 1910.

W Clyde Jones and R. S. Taylor, for appellant.

C. A Brown, for appellees.

This suit was brought in the court below for alleged infringement of certain letters patent. The appellant was complainant below; and the appellees, the defendants below, comprise the Dean Electric Company and certain of its officers. The patent in suit was applied for by William W. Dean as inventor, who subsequently assigned his invention to appellant; and thereafter letters patent No. 722,212 were issued in favor of William W. Dean, assignor of appellant, and were delivered to it on the day of their issue, March 10, 1903. The invention is called 'an improvement in subscriber's telephone circuits. ' The inventor who assigned his invention to appellant appears to be the vice president and chief engineer of the appellee company. In addition to the usual averments and denials of pleadings in patent cases, the answer contains denials of both patentability and infringement of the patent in suit, and also contains allegations that more than two years prior to the date of Dean's application for the patent in suit the same device, or substantial parts thereof were patented, described, and shown in various letters patent therein mentioned, and, furthermore, that the invention of Dean as claimed under letters patent No. 722,212 'was abandoned and dedicated to the public by reason of its description and publication by him or a substantial and material part or parts thereof' in certain of his prior letters patent therein referred to, or that the patent in suit 'constitutes mere double patenting of the improvements set forth in said letters patent' so referred to.

The alleged infringing device is made according to an invention claimed under letters patent issued to Ray H. Manson, assignor of the appellee company, No. 818,897, dated April 24, 1906, and purporting to be 'improvements in telephone systems.' The case was tried below upon a vast amount of evidence offered by both sides. The court found that there was no infringement and dismissed the bill, with costs. The case is pending here on appeal.

Before SEVERENS and WARRINGTON, Circuit Judges, and KNAPPEN, District judge.

WARRINGTON Circuit Judge (after stating the facts as above).

There are two assignments of error. One concerns the finding of noninfringement and the other the dismissal of the bill. In its opinion the court below considered only the question of infringement. It was found that the operation of the invention in suit and the alleged infringing device involved separate and distinct principles of physics, and it was held that there was no infringement for that reason.

Both of the inventions relate to substations in telephone systems of the central energy type; that is, they relate to the places and apparatus occupied and used by the subscribers in systems supplied with current from batteries common to all and located at the central stations. While it is claimed that each patent embraces a number of elements in combination, yet the central feature in each is the placing of the receiver in a path designed for the voice currents and out of the path designed for the energizing current. The voice currents are imposed on the battery current by the vibrations of the diaphragm of the microphone, when speaking into it. The undulations so created are usually described as waves of varying forms and frequency, like a ripple caused by the action of the wind upon the surface of a body of water. The undisturbed portion of the battery current, called the 'energizing current,' thus both comprises and carries the voice currents. The energizing current is steady; the voice currents are unsteady. Prof. Carhart, one of the witnesses, aptly describes the energizing and voice currents thus:

'When two subscribers are connected for conversation in a central energy system and conversation is in progress, a steady current, used for transmitting signals and for operating the carbon transmitter, flows over the connecting line. Superposed on this steady current are undulations, irregular in form and varying in frequency, which alone transmit the conversation and are called 'voice currents.' Hence the current flowing over the line is a combination of a steady current and an alternating one. It may be roughly illustrated by a continuous band saw, the uniform or unbroken width of which illustrates the steady current, and the teeth the alternating current.'

The devices of the patentees, Dean and Manson, were contrived for so separating the voice currents from the steady current at the substations as to avoid certain specified objectionable features of existing telephone systems and at the same time to keep the receiver in the direct path of the voice currents. To turn again to the simile of the band saw, Prof. Carhart said further:

'Now the problem was to shear off, so to speak, the ragged edge of the band and send it as an alternating current through the receiving telephone, while the continuous part of the current is carried through another portion of the substation apparatus and thence, together with the alternating part, through the carbon transmitter.'

We may now consider what Dean did, and what advance, if any, he made over the existing art. After stating in substance, in the descriptive portion of the letters patent, that it had been the common practice to include the telephone receiver in series with the microphone so that the energizing current would pass through both, and that this was objectionable for various reasons-- such as reversal in polarity of the sources of energy through reversal of the line wires by linemen and so demagnetizing the permanent magnet of the receiver, also that in such systems the coils of the receiver must be made of larger wire than necessary for the talking currents, and that the passage of the energizing current through the coils subjected the diaphragm to a constant pull or tension requiring increased rigidity thereof and considerable air space between it and the ends of the magnet poles, and 'thereby decreasing the efficiency of the receiver'-- Dean said:

'It is the object of the present invention to remove the receiver entirely from the influence of the energizing current traversing the microphone, whereby the several objections above enumerated are obviated.

'In accordance with the present invention the receiver is included in a path which is opaque to the passage of the energizing current, which is usually continuous, while a parallel path is provided around the receiver which is opaque to the passage of the talking currents, while permitting the energizing current to freely pass therethrough. In practice I usually include a condenser in the path containing the receiver and an impedance or choking coil in the path which is parallel thereto.'

He then displays his invention by two diagrams: Fig. 1 illustrating a system embodying his invention, and Fig. 2 a modification thereof. It is not necessary to present the latter diagram. Fig. 1 is as follows:

(Image Omitted)

He then states:

'I have illustrated in Fig. 1 two telephone lines embodying my invention in connection with central-station apparatus of well-known form. When the subscribers are connected for conversation, the central battery, r, is adapted to send current over the limbs, a a', of the telephone line. When the receiver, f', is removed from the switch hook, f2, the same engages contacts 7 and 8. The microphone, f, is shown as connected between the contact, 8, and the limb, a, while the switch hook, f2, is connected with the limb, a'. The receiver, f', is connected with the contact, 7, in circuit with the condenser, 1. An impedance or choking coil, k, is interposed in the parallel path around the receiver, f'. The bell, f3, may be connected between the limb, a, and the parallel path containing the receiver, so that the bell will be in circuit with the condenser, 1.

'The condenser, 1, renders the path containing the receiver opaque to the passage of energizing current from the battery, r, and consequently the energizing current does not traverse the coils of the receiver. The energizing current may, however, freely pass through the parallel path containing the impedance coil, k, since said coil interposes but slight resistance to the passage of a continuous current. The impedance coil prevents the passage of the talking currents, which are thus choked back and caused to pass through the condenser, 1, and the receiver, f'. The bell, f3, should be of high resistance-- say of one thousand ohms resistance-- so that the talking currents and the energizing current will not readily pass therethrough.

'When the receiver is upon the hook, the hook, f2, rests out of contact with the contacts, 7 and 8, and the circuit through the receiver and the microphone is thus opened. Calling current sent from the central station will traverse the condenser, 1, and bell, f3. When the subscriber responds and lifts his telephone from the hook, the current from the energizing battery, r, is closed over limb, a, microphone, f contact, 8, switch hook, f2, through coil, k, and limb, a', back to the battery. The condenser, 1, prevents the passage of the energizing current through the receiver, f'. Talking currents repeated through the repeating coil at the central station pass over limb, a, through microphone, f, contact, 8, switch hook, f2, contact, 7, thence through the receiver, f', and condenser, 1, to limb, a', and back to the central station. The impedance coil, k, prevents the passage of the talking currents therethrough, thereby...