Codex Corp. v. Milgo Electronic Corp., s. 82-1644
| Decision Date | 02 August 1983 |
| Docket Number | Nos. 82-1644,83-1076 and 82-1707,s. 82-1644 |
| Citation | 219 USPQ 499,717 F.2d 622 |
| Parties | CODEX CORPORATION, et al., Plaintiffs, Appellees, v. MILGO ELECTRONIC CORPORATION, et al., Defendants, Appellants. CODEX CORPORATION, et al., Plaintiffs, Appellants, v. MILGO ELECTRONIC CORPORATION, et al., Defendants, Appellees. |
| Court | U.S. Court of Appeals — First Circuit |
Allen Kirkpatrick, Washington, D.C., with whom Larry S. Nixon, Cushman, Darby & Cushman, Washington, D.C., Marcus E. Cohn, P.C., David H. Gibbs, Boston, Mass., Peabody & Brown, Boston, Mass., Harold L. Jackson, Albin H. Gess, and Jackson Jones & Price, Tustin, Cal., were on brief, for Milgo Electronic Corp., et al.
Paul F. Ware, Jr., Boston, Mass., with whom Goodwin, Procter & Hoar, Robert E. Hillman, G. Roger Lee, William E. Booth, and Fish & Richardson, Boston, Mass., were on brief, for Codex Corp.
Before CAMPBELL, Chief Judge, BOWNES, Circuit Judge, and RE, * Chief Judge.
Milgo Electronic Corporation and International Communication (Milgo) appeal from an adverse declaratory judgment in a patent validity action brought by Codex Corporation and Yellow Freight Systems, Inc. (Codex). Codex cross-appeals because of the failure of the district court to grant all of the relief it sought and on the ground that the amount of attorney fees awarded it was too low. The district court opinion is reported, Codex Corp. v. Milgo Electronic Corp., 534 F.Supp. 418, 432 (D.Mass.1982).
The dispute revolves around three patents, all owned by Milgo as assignee:
(1) No. 3,524,023, Sang Y. Whang, inventor, Band Limited Telephone Line Data Communication System (Whang '023);
All computer machine languages operate on a binary number system. This system or language involves only two elements: positive or negative or, most commonly, 1 or 0.
Computers do not always operate alone; some are built to communicate with other computers. In order for one computer to talk with another some sort of communication link has to be established. At the time the patents in this case were issued the primary communication link was direct distance dialed telephone lines (DDD). Unfortunately for talking computers, binary or digital data cannot be transmitted over DDD lines rapidly and reliably. To transmit information through DDD lines the transmission must be made in an analog form. This analog transmission is best thought of in terms of a sinusoidal waveform (sine wave) as illustrated below:
NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE
The above illustration shows a sine wave with an amplitude of one and a cycle duration of T seconds. Both of these terms will be explored in some detail later.
For computers to talk one with the other it is necessary to transform digital signals to analog at the transmitting computer and back again at the receiving computer. This transformation is accomplished in both instances by a modem.
The word "modem" is short for modulator-demodulator. Modulation is the alteration of the sine wave in some manner so as to impart some information to it. For the purposes of this litigation modulation can take one of three forms: phase modulation, amplitude modulation, or a combination of both phase and amplitude modulation.
Phase modulation, or more specifically in this case differential phase modulation, is accomplished by sending out a signal pulse during a modulation period followed by another modulation period with a signal pulse of a different phase. The receiving modem detects this phase shift which contains the information in each signal pulse.
Amplitude modulation is accomplished in the transmitting modem by changing the amplitude of the sinusoidal sine wave from one modulation period to the next. The receiving modem detects this change in amplitude thus reading the information contained in the signal pulse. The combination of phase and amplitude modulation is accomplished by changing both the phase and amplitude of the sine wave from one modulation period to the next.
The speed at which information can be transmitted depends primarily on two factors. First, it depends on the number of signal pulses (bauds) that can be transmitted per second, and secondly, it depends on the number of discrete "bits" of binary data (1 or 0) that can be encoded in each baud (bits per baud).
A problem with analog signal transmission is that some distortion of the signal is bound to occur; the received signal is not going to be identical to the one transmitted. This distortion is a function of two characteristics, one of the signal, the other of the DDD line itself.
The problem with the DDD line is that at the upper and lower ends of the frequency range available the analog signal is susceptible to amplitude and delay distortion. These distortions are fatal to fast and accurate transmission of information. It was well-known in the early 1960's that at the center of this available frequency range there existed a "sweet spot." The sweet spot is a band of about 1000 Hz 1 in a range between the frequencies of 1200 Hz and 2200 Hz which has the characteristic of being relatively free from distortions.
The problem with the signal occurs when it is modulated. Modulation causes a dispersal of energy up and down the frequency spectrum. This energy, outside of the sweet spot, is susceptible to delay and amplitude distortion. The delayed reception of this energy by the receiving modem will distort the apparent phase and amplitude of the received signal causing inaccurate decoding of the information.
To solve this problem of energy dispersal over the frequency spectrum a composite filter to filter out energy at all but the desired frequencies is used. This solution, however, causes its own problem, it spreads the signal out over time. The energy representing the signal in one baud is smeared in time so that some of it is still "ringing" or echoing in the bauds that succeed it. This ringing causes intersymbol interference or confusion from one baud to the next. The next step was to solve this problem.
In 1928 Harry Nyquist published his discovery that an information carrying pulse, or baud, of duration in time of T seconds required a bandwidth of 1/T Hz for accurate transmission. This basic constraint on the bandwidth is crucial to mitigating the intersymbol interference.
Nyquist went on to describe a filter which would accomplish this. The ideal Nyquist filter, called "brickwall," passes only this 1/T bandwidth. It was recognized that the actual construction of such a brickwall filter was not possible. Practical filter design requires the use of filters with a roll-off of greater than zero. The diagram and text which follows illustrates both the brickwall filter and the concept of roll-off.
The carrier frequency (fc ) is the frequency of the sine wave which is modulated by the modem to produce the information-carrying signal pulse. The portions of the bell-shaped curve that extend beyond the brick wall are known as the skirts. One way of defining the roll-off of the filter is by taking the ratio of the width of the skirt along the abscissa to the width of the Nyquist ideal of 1/T Hz. A composite filter exhibits 50% roll-off when the sum of the skirts is 1/2T Hz. It should also be noted that to meet Nyquist's criteria a roll-off of 100% is the maximum allowable.
One further necessary element of modem design is a mechanism for determining when a baud begins and ends. Concomitant with that determination is the need to know when or where to read the information contained in a baud. The mechanism for determining when to sample or read the information contained in a baud is called "clock" in the present art. It is a characteristic of the 1/T bandpass filter that the energy of the signal pulse will be minimum at the beginning of the pulse, build to a maximum at approximately the middle of the pulse, and then decay to a minimum point at the end of the pulse. It is this characteristic that permits clock recovery by the receiving modem. This allows the receiving modem to read the information at the center of each signal pulse. Nyquist revealed that with a 1/T bandpass filter the interference or ringing caused by one baud would be zero at the center of the succeeding baud. Thus, the concept of center sampling was born; the idea being to read the information encoded in a baud as close as practicable to the center of each baud.
The presence of echo suppressors on the DDD lines present yet another problem to modem designers. Echo suppressors permit signals to be transmitted in only one direction at a time, the preference being given to the stronger signal. It is a characteristic of DDD lines and associated amplifiers that if echo suppressors were not present the telephone user would hear echoes of his own voice. The problem with the echo suppressors is that they take 100 milliseconds to reverse direction or turn around. This means that once the first party stops talking and the second party starts it takes 100 milliseconds before the echo suppressor will pass on the second party's speech energy. For spoken communication a 100 millisecond turnaround delay is no problem. For data communications a 100 millisecond turnaround delay is intolerable.
The solution to this problem is to disable or turn off the echo suppressors by putting a tone on the line. It was well recognized in the early 1960's that echo suppressors once disabled would remain disabled as long as there was energy on the line. This could be accomplished by a signal transmitted at a frequency other than the frequency of the main...
To continue reading
Request your trial
-
Lyle/Carlstrom Assoc. v. Manhattan Store Interiors
...Mueller v. Campbell, 68 F.Supp. 464 (D.Ohio 1946), or relevant prior art was not disclosed to the PTO, Codex Corp. v. Milgo Electronic Corp., 717 F.2d 622 (1st Cir. 1983), cert. denied, 466 U.S. 931, 104 S.Ct. 1719, 80 L.Ed.2d 191 (1984), particularly if the subsequent disclosure of prior a......
-
Pascoag Reservoir & Dam, LLC v. Rhode Island
...rights for twenty-six years offends the notion that a party must come to an equity court with clean hands. See Codex Corp. v. Milgo Elec. Corp., 717 F.2d 622, 633 (1st Cir.1983) ("The maxim of `he who comes into equity must come with clean hands' of necessity gives wide range to a court's u......
-
Rodriguez Rodriguez v. Munoz Munoz, 85-1215
...not first presented to the district court. See United States v. Ven-Fuel, 758 F.2d 741, 760 (1st Cir.1985); Codex Corp. v. Milgo Electronic Corp., 717 F.2d 622, 629 (1st Cir.), cert. denied, 466 U.S. 931, 104 S.Ct. 1719, 80 L.Ed.2d 191 (1983). Upon consideration, we believe this to be one o......
-
Tamko Roofing Products v. Ideal Roofing
...8 (1st Cir.1981), in the context of determining whether the losing party has engaged in "inequitable conduct," Codex Corp. v. Milgo Elec. Corp., 717 F.2d 622, 630 (1st Cir.1983). The language of the two acts is identical; what is different is that here we have the benefit of the Lanham Act'......