Showing papers on "Clock synchronization published in 1971"

Remote clock synchronization system

Abstract: A system for the precise synchronization of high frequency electronic clocks by providing each station other than the master station with a tracking circuit. The tracking circuit consists of an early gate generated just prior to the arrival of the synchronizing pulse from the master station and a late gate generated just after the synchronizing pulse is received from the master station. If the synchronizing pulse received from the master station is either late or early the clock will either speed up or slow down so that it will be in synchronization with the synchronizing pulses received from the master station.

One-Way Time Synchronization via Geostationary Satellites at UHF

Abstract: This paper describes an experiment designed to evaluate the accuracy of one-way clock synchronization using geostationary satellites with the propagation delays calculated from the satellite's orbital elements. Propagation delays from a ground transmitter via satellite to each of five locations in the North and South American continents were measured and compared with the calculated values. Three months of data are presented along with descriptions of the equipment, timing signal format, and methods for delay calculation and time recovery. The results show that within two weeks of epoch for the orbital elements, clocks can be synchronized to 150 ??s using the Tactical Communications Satellite (TACSAT). If one of the observers of the timing signals was already synchronized to the master clock, his delay measurement could improve the results for TACSAT to 75 ??s. By the same method and within 12 hours of epoch, the results for the Lincoln Experimental Satellite-6 (LES-6) indicated that synchronization to 25 ??s was possible.

Clock Synchronization from Satellite Tracking

Abstract: The tracking of synchronous satellites to provide propagation delays for the synchronization of clocks is described. The tracking is accomplished by range measurements to the satellite from three stations using signals transponded by the satellite. These same signals also functioned as the timing signals for the synchronization of other stations' clocks. Although the range measurements were of low resolution by usual standards, approximately 3000 meters, they provided the delays necessary to synchronize clocks to 40 microseconds or better. These results were obtained over a 4-month period using two satellites with measurements from five stations in the United States and South America.

Redundant aircraft clock synchronization

Abstract: An air traffic system in which participating aircraft occupy uniquely assigned time slots and have first time clock means which are assumed to be already finely synchronized to a groundbased master time clock by signal exchanges with ground stations and have second time keeping means in each aircraft which are synchronized first to the master time clock and are thereafter further and more finely synchronized to other aircraft nearby, to provide a desirable degree of redundancy while also remaining within the limits of the ground station imposed synchronization. Each aircraft in the illustrative embodiment selects by time-slot designation another nearby aircraft as its synchronizor, and in addition also responds to requests for synchronization by other synchronizee aircraft identified by other time-slot selection. This redundant fine synchronization among nearby synchronizor and synchronizee aircraft is especially useful in situations where large numbers of aircraft are flown close together in formations, or in groupings of commuter aircraft, for instance, in which STOL aircraft fly between cities close together, perhaps one behind the other.

Conversion of nrz data to self-clocking data

Abstract: An improved digital encoder and decoder for high density magnetic recording. An NRZ code and clock are combined in a single encoded signal to provide a Pouliart code. The encoder provides a simple straightforward encoding logic; the decoder includes an analog slope detector/comparator to detect flux transitions and means to correct an erroneous clock synchronization.