653 5 Findings of Fact miles per second. This is approximately 10 to 11 microseconds per mile for the transmission of a radio signal out to the target and back again. The transmitting pulses sent out by the transmitter in the defendant's structures in issue have a duration of eight-tenths of a microsecond. These pulses are repeated at a periodic rate of 1,707 per second. After each pulse has been transmitted the transmitter is quiescent and the receiving system awaits the reception of an echo for a period of 586 microseconds. 6 All these various time intervals are precisely controlled by what a layman would call a master clock. In the sets here in issue this consists of a crystal-controlled oscillator circuit which produces a master timing frequency of 81.95 kilocycles (81,950 cycles per second). This master frequency is further modified into various other multiple time intervals by electronic circuits, which are termed "multivibrators". A mechanical analogy is found in a watch in which the hour, minute and second hands are driven in multiple relationship by a single balance wheel. The electronic circuits associated with the control of the various time intervals not only function to produce the pulses at properly spaced time intervals but, in addition, determine the duration of the various pulses and also their contour or wave shape. 29. The present issue relates to that portion of the electronic timing circuits that receives two different pulses from the multivibrator circuits and combines them (both as to contour and time) to form the pulse which periodically operates the transmitter and certain other components of the system every 586 microseconds. There has been introduced in evidence as plaintiffs' exhibit 10 a circuit diagram illustrating the circuits here involved, and the circuit diagram illustrated herewith and entitled "Defendant's alleged infringing circuits" has been taken from this exhibit. "One-millionth of a second. A quartz crystal incorporated in an electronic oscillating circuit has the property of accurately controlling the oscillations of that circuit. The rate of oscillation is dependent upon the thickness to which the crystal is ground and certain other characteristics of the crystal. As shown in this diagram, two electronic tubes are used in this portion of the circuit. The left-hand tube, identified by the legend "V613B," is a conventional triode having a plate, grid and cathode. This tube is so connected as to receive its input signal between the grid and plate and to deliver a positive output signal from its cathode, thus functioning as a cathode follower, the voltage produced on the cathode following the voltage of the grid up and down and in phase therewith. The plate of this tube is connected to a D. C. source of 250 volts. The right-hand tube, identified by the reference character V-614, is a tube having five elements, viz, a plate, a cathode, and three grids. In the present instance we are only concerned with the two lower grids designated 4 and 6. The plate circuit of this tube is supplied with plate current through a resistance from a voltage source of 250 volts. The cathode 3 of the first tube or cathode follower is connected to one terminal of a blocking or isolating condenser C 659 of .01 microfarads, the other terminal of which is connected to the second grid 6 of the right-hand tube. This condenser presents an infinite impedance to direct current flow and thus 653 Findings of Fact permits a negative bias voltage of 20 volts to be applied to this grid through the resistor R689. The application of this negative voltage to grid 6 of the tube V-614 enables this grid to be biased beyond the point of cutoff so that normally no current will flow in the plate circuit. Similarly, the lower grid 4, which is also isolated from its input circuit by the condenser C 657 has a normal negative bias of 9 volts applied to it through the resistor R 690. This negative voltage is sufficient to bias this grid beyond the point of cutoff so that no current will flow through the plate circuit of the tube. That is to say, if the grids 4 and 6 are contemplated as mechanical gates within the tube, the negative bias voltages applied to and normally maintained on them are sufficient to keep each tightly closed and not permit any current flow in the plate circuit of the tube. 30. Every 586 microseconds a pulse of approximately square wave shape and 6 microseconds in duration, is fed into the grid of the first or cathode follower tube from the multivibrator system. This produces a strong positive pulse of similar shape on the cathode of this tube. At this repetition frequency, which is 1.707 kilocycles, the isolating condenser presents an impedance of 9,350 ohms and therefore permits the recurring square wave pulses to pass therethrough and to the second grid 6 of the second tube. On each pulse, grid 6 swings from the 20-volt negative bias to approximately 40 to 100 volts positive. In terms of the previous mechanical analogy of a gate, grid 6 is suddenly swung from a tightly closed position to a wide-open position every 586 microseconds for a period of 6 microseconds. The approximate qualitative shape of these trigger gate pulses is shown in the top line of the figure herewith reproduced from the Service Manual, plaintiffs' exhibit 9, which figure is entitled "Trigger gate and selector waveforms", as shown on page 21. The lower grid, designated 4, of the right-hand tube is continuously receiving an input from the multivibrator system which has a contour approximating that of a sine wave. These are produced in the multivibrator system at a rate of 81.95 kilocycles which spaces individual pulses 12.2 microseconds apart. This input is shown in the second line of the above figure, the individual pulses being designated thereon as trigger pips. The voltage value of the narrow curved portion of the peaks is of sufficient value to overcome the 9 volts negative bias of grid 4 of the second tube. This action is shown in the second line of the above diagram. As the bias on each of the grids 4 and 6 is sufficient to independently hold the tube in a nonconductive state, no current will flow in the plate circuit until both biases are simultaneously overcome. Again referring to the mechanical analogy, either gate 4 or 6 can be opened but as long as the other gate remains closed no plate current can flow through the tube. However, every forty-eighth trigger pip is fed to grid 4 at the same time that a positive trigger gate pulse occurs on grid 6. When this occurs and in the brief interval of time (approximately 1 to 2 microseconds) that the top curved portion of the sine wave forming the trigger pips rises above the cutoff value of 9 volts, the tube V-614 swings from a negative cutoff with zero current flow and heavily conducts, producing in its plate circuit a negative going pulse of approximately 1 to 2 microseconds having a steep or approximately vertical wave front. Such pulse is illustrated in the bottom line of the above-referred-to diagram of wave forms. 653 Findings of Fact This is the pulse that triggers or energizes the transmitter and other associated devices. The right-hand tube of the circuit under discussion operates as a pulse-forming tube, the output pulse of which is formed by the coincidence of two different input pulses, both of different shapes and contours, neither of which is reproduced in the output circuit. In forming the output pulse, the tube swings from a nonconductive condition (biased beyond cutoff) to a full conductive condition and back again. 31. In the defendant's circuit the first tube functions as a cathode follower in presenting a low-impedance source for the 6-microsecond positive pulses fed to the second grid 6 of the second or pulse-forming tube. In this sense there is a compensating action present in the first tube of the defendant's circuits. With respect to such compensating action, the Service Manual (plaintiffs' exhibit 9) states on page 51 thereof as follows: (12) Trigger gate cathode follower. V613B makes the positive selector gate available to the trigger selector stage from a low-impedance source and prevents loading of V612. The positive selector gate output is fed to the screen grid of trigger selector V614. Tube V612 (not shown above) is the source of the 6-microsecond pulse wave which is fed to the grid of the cathode follower tube. The cathode follower tube compensates to supply an ample 6-microsecond positive pulse to the pulse-forming tube, ample in the sense that when the pulse-forming tube is called upon to form the trigger pulse for the transmitter, its plate circuit will be made fully conductive. The second tube of defendant's circuit is not an amplifying tube, and the problem of distortionless amplification is not present. Still referring to the analogy of a gate in connection with the operation of grid 6 of this tube, this gate is alternately kicked wide open and then slammed shut by the gate tender (the 6-microsecond timing pulse). In contradistinction, the gate (grid) of an amplifying tube is always open (operated above cutoff) and is opened or closed more or less by the hands of a maestro in exact accordance with a musical score (the input voltage to the grid) which he faith 911794-51-45 |