Showing papers on "Master clock published in 1968"

Time synchronization from Loran-C

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.

Worldwide Clock Synchronization Using a Synchronous Satellite

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.

Transmission of asynchronous telegraphic signals

Abstract: In transmitting telegraphic signals, binary asynchronous signals are scanned at regular intervals and combined to form scanning groups, each of which is converted to a code word. The data contained in the code word is then transmitted via a telegraphy channel to the receiving end of the line where it is converted to a binary time-quantitized output signal. The circuit for performing these operations has a transmitter part and a receiver part. The transmitter part has a master clock, for transmitting different pulse series for controlling the scanning and transmission, a channel unit for scanning the signal and a code converter for converting the scanning group into a code word. The receiver part has a master clock synchronized by the received signals, a counter for counting pulses corresponding to the scanning pulses and an output flip-flop.

A Synchronous Sweep Frequency Oscillator

Abstract: This paper describes a linear frequency sweep oscillator which is accurately controlled by a master clock. The voltage controlled oscillator which generates the frequency sweep is first phase-locked to the master clock. Then, a ramp generator drives the voltage controlled oscillator over the required frequency range, while a phase-sampling loop controls the instantaneous frequency to the desired ramp accuracy. The phase-sampling control loop is synchronized to the master oscillator by the sampling rate, which is derived directly from the master clock frequency. A laboratory system constructed on these principles sweeps from 2.095 MHz to 2.320 MHz in approximately 1.709 seconds, with a deviation from linearity of less than ±75 Hz.

Extended range clock synchronization for collision avoidance system

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.