Showing papers on "Clock synchronization published in 1968"
TL;DR: In this article, the authors discuss the timing capabilities of Loran-C and illustrate the techniques that are used for the derivation of time and frequency for long-range radio systems.
Abstract: Loran-C navigational transmissions, at a frequency of 100 kHz, can be used to provide clock synchronization over long distances to accuracies within ±1 ?s. Results to date represent improvements as great as three magnitudes over other operational long-range radio systems. This article discusses the timing capabilities of Loran-C and illustrates the techniques that are used for the derivation of time and frequency.
37 citations
Patent•
21 Nov 1968
TL;DR: In this article, a system for the generation of clock signals in a data processing apparatus is described, in which the clock signals are developed from a source of higher frequency pulses and applied to an apparatus in which data signals are represented in a non-return-to-zero (NRZ) manner, and the clock signal are synchronized to the occurrence of changes in data item representation.
Abstract: A system for the generation of clock signals in a data processing apparatus is disclosed, in which the clock signals are developed from a source of higher frequency pulses. The clock signals are applied to an apparatus in which data signals are represented in nonreturn-to-zero (NRZ) manner, and the clock signals are synchronized to the occurrence of changes in data item representation. It is recognized that the synchronization of the signals may vary and, in particular that there is a condition of spurious synchronization in which the clock signals may occur 180* out of phase with data changes. The system proposed is arranged to recognize both variations in synchronism and the spurious synchronism condition and to correct the relative timing between clock and data change signals to bring the system into true synchronism by modifying the application of the higher frequency pulses to a clock signal generating countdown arrangement.
16 citations
TL;DR: In this article, one-way VHF timing signals were relayed to remote clocks from a reference clock by means of a transponder on a geostationary satellite, and the accuracy of predicting the radio propagation delay was 10 As or 60 Ms depending on the method used.
Abstract: An experiment performed in late 1967 is reported which investigated the synchronization of widely separated clocks. One-way VHF timing signals were relayed to remote clocks from a reference clock by means of a transponder on a geostationary satellite. The problem of synchronizing clocks using one-way transmission reduces to the problem of predicting the radio propagation delay. The accuracy of predicting the delay was 10 As or 60 Ms depending on the method used. This technique may offer an alternative to transporting atomic standards to geodetic and spacecraft tracking stations around the world in fulfillment of their clock synchronization requirements.
14 citations
Patent•
16 Sep 1968TL;DR: In this article, a cooperative collision avoidance system is proposed to synchronize the clock without addressing within a cooperative system, which utilizes the time slot of the aircraft requesting synchronization during its time slot.
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.
6 citations
Patent•
03 Dec 1968TL;DR: In this paper, the authors propose an approach for synchronizing clocks within a cooperative collision avoidance network where an aircraft after operating in an isolated environment for a predetermined time sets its clock in a standby position and listens for start of epoch signals.
Abstract: Apparatus for synchronizing clocks within a cooperative collision avoidance network wherein an aircraft after operating in an isolated environment for a predetermined time sets its clock in a standby position and listens for start of epoch signals. Upon hearing a start of epoch signal the aircraft immediately starts its clock and begins counting epochs and the time slots contained therein. During own time slot, as determined by its clock, the aircraft transmits a clock synchronization request. If no synchronization responses are received the aircraft will automatically advance its clock by a predetermined amount and once again transmit a synchronization request during its next time slot. If a synchronization response is now received the aircraft will synchronize its clock taking into account the amount of time by which its clock had to be advanced in order to receive the synchronization response. If no response is received the aircraft automatically returns its clock to the standby condition.
1 citations