Abstract: Interstation synchronization apparatus for a time division multiplex communication system having a plurality of communication stations is provided wherein multi-input, phasecontrolled oscillator means, whose output signal represents the station synchronization signal, is present at each station therein. The multi-input, phase-controlled oscillator means is synchronized by a comparison of the synchronization signal generated thereby with synchronization signals generated at stations remotely located therefrom. The multi-input phasecontrolled oscillator means is compensated for phase lags present in the externally generated synchronization signals as applied thereto by discrete signal levels introduced therein to control the frequency of the output signal thereof.

Abstract: The notion of an extended cyclic code has recently been formulated. It is known that, subject to certain polynomial constraints, certain random-error-correcting cyclic codes can be extended to form codes capable of automatically recovering from synchronization losses. It is shown in this paper that the above-mentioned constraints are unnecessary and that this synchronization recovery technique can be used with any additive-error-correcting cyclic code.

Abstract: T HAS been shown that many rodent species behave rhythmically even in a constant environment (summaries or extensive examples in Rawson, 1959; Justice, 1960; Pittendrigh, 1960; DeCoursey, 1961, 1964; Aschoff, 1963; Hoffmann, 1965). Such rhythms are believed to arise in the animal endogenously without external periodic stimuli. Individual rhythmic frequency usually differs from the natural day cycle and must be entrained to the 24-hr cycle of the physical environment if the animal is to operate successfully in nature. Synchronization of the internal rhythm with the external world is brought about in the animal by utilization of periodically repeated environmental factors called entraining agents, clues, synchronizers, or Zeitgeber (DeCoursey, 1960; Aschoff, 1963; Enright, 1965; Pittendrigh, 1965). Many experiments have shown the natural 24-hr cyclic fluctuation in light intensity to be the primary factor maintaining the endogenous rhythm of an animal in proper phase with its environment (reviews in Pittendrigh, 1960, 1965). In striking contrast, experimental thermal cycles have not been effective in the entrainment of endogenous circadian rhythms to the natural day. The question is here examined in the rock pocket mouse, Perognathus intermedius, a small heteromyid rodent restricted to the extreme arid regions of southwestern United States. This species is exposed regularly to great daily fluctuation in temperature, thus suggesting the possibility that temperature cycles might contribute to or replace the regulatory action of light. This species has also been of particular interest to ecologists because of two principal color forms. The black subspecies (or color variety), P. i. ater, is found, among other localities, on the black Malpais Lava Beds in the Tularosa Basin, New Mexico, while the paler form, and more usual color variety, P. i. intermedius, occurs on light-colored rocky outcrops marginal to the valley and but a few miles distant from the lava-bed population. Dice (1930), Bradt (1932), and Benson (1933) have suggested that matching of pelage color to that of the substrate upon which the populations reside has evolved as a consequence of differential predation and natural selection. Species of Perognathus have long been considered nocturnal; however, the mechanism for exact color matching, as opposed to grayness matching, in a 1We are grateful for support provided by the National Science Foundation (Grant No. G23564, W. G. R.; Summer Research Fellowship, M. C. S.) and the Research Committee of the University of Wisconsin Graduate School. Figures have been provided by Miss Cheryl Hughes. We are most grateful to Dr. P. J. DeCoursey for commentary on the original activity records. The experiments were carried out primarily by the senior author; the results were submitted in partial fulfilment of the degree of Master of Science at the University of Wisconsin. The junior author guided and participated in the experimentation and, with the generous editorial criticism of Dr. DeCoursey, has prepared the present paper.

Abstract: A means of synchronizing clocks without addressing within a cooperative collision avoidance system which utilizes the time slot of the aircraft requesting synchronization. During its time slot, an aircraft transmitting a collision avoidance message automatically requests clock synchronization. All other aircraft within the collision avoidance network which receive the synchronization request will respond in a random manner with a probability inversely proportional to the number of potential responding aircraft within the collision avoidance network. To accomplish this each cooperating aircraft is equipped to monitor the number of occupied time slots so as to determine the number of potential responding aircraft, determines the probability of its response with respect thereto and determines in accordance with the probability thus derived whether it should respond to this particular synchronization request.

Abstract: THE INVENTION ENCOMPASSES A SYNCHRONOUS TIMING SYSTEM OF THE TYPE WHEREIN A COUNTER IS "SLAVED" TO A SYNCHRONIZATION STATION BY COUNT PULSES AND RESET SIGNALS. BY PROVIDING A SYNCHRONIZATION SIGNAL HAVING ONE LESS PULSE THAN THE CAPACITY OF THE COUNTER, AND USING THE ABSENCE OF THE PULSE TO PROVIDE THE SYNCHRONIZATION INTELLIGENCE, THE SYSTEM HAS A BUILT-IN FEATURE ALLOWING DETECTION OF SYNCHRONIZATION FAILURE.

Abstract: The collision avoidance synchronization system provides a method by which over 1000 aircraft can be accommodated in a 250-mile radius. Information is exchanged at a data rate of once every 3 seconds. Master-time synchronization permits one-way ranging between aircraft with an rms range error of less than 120 feet (36.6 meters) when both use the same master. A maximum error of less than 1000 feet (304.8 meters) rms between two aircraft occurs when each is tied back to a different master and each is at the limits of a hierarchy air-to-air synchronization extension system. An asynchronous backup mode of operation is provided to permit system operation in low-density areas beyond coverage of the master system time.

Abstract: : A compilation of transmitter outages and synchronization errors in the Omega System from the beginning of modern operation in January 1966 through June 1968 is presented together with an historical review of operation and discussion of synchronization. (Author)

Abstract: A forced system described by the differential equation: x\" + ef(x, x') + ulx = F cos iot is considered for cases where (n/m)u is close to w0 . (Here m and n are integers and n/m > 1 denotes superharmonic while n/m < 1 denotes subharmonics.) If the unforced system (F = 0) is conservative, the forced system is shown to possess an integral constraint and the solution is reduced to quadratures, even though the force adds or removes energy from the oscillations. Furthermore, the suband superharmonic cases where the n/m ratios are inverse are shown to be intimately related, and results for one can be deduced from the other by appropriate interchange of variables. For systems which are nonconservative (when F = 0), there is a general class, including the frequently discussed Van der Pol oscillator, whose members are mathematical duals of appropriate conservative systems with added linear dissipation. Both the nonconservative system and its \"conservative\" dual are forced. The duality consists of an interchange of the roles of the dissipation and detuning between the systems and yields a pair of phase portraits with singularities located at identical points and orthogonal phase trajectories. Examples for polynomial nonlinearities are given and in considerable detail for the power 5.

Abstract: Spacecraft carrying large numbers of scientific instruments are presently transmitting data at the rate of approximately 100 million data points per day. The outputs of the sensors are partially processed on the spacecraft and transmitted to the ground. These data must then be converted from raw digital form into a conceptually meaningful form which the experimenters can analyze and from which they can draw valid conclusions about the phenomena being measured. At present the ground processing is done in several steps. The first includes conversion of the raw data acquisition station tapes into computer tapes and includes signal clean-up, establishment of synchronization, and time decoding. In the newest processing lines this first step also includes a moderate amount of editing and quality control. The rest of the steps involve large scale computers and include further editing, establishment of accurate timing, computation of the spacecraft attitude, and sorting, to provide data tapes for the individual experimenters. The experimenters have the responsibility for the further reduction to more meaningful form. These operations include further sorting, storage, compilation, computation, and display. There is at present a great need for additional development of analysis and display programs, techniques, and equipment to assist in this work.