Showing papers on "Master clock published in 1974"

PCM synchronization and multiplexing system

Abstract: A system for communicating digital data which utilizes a synchronization eme in which a transmitter transmits a binary 1 followed by n data bits which are followed by n + 1 binary 0's and in which a receiver is synchronized with the transmitter by generation of a master clock in response to receipt of the transmitted binary 1 and by initiation of a frame pulse having a pulse duration equal to the duration of the incoming data frame.

An all-digital Manchester symbol synchronizer for Space Shuttle

Abstract: The Shuttle S-Band relay communications links via TDRS are coded and may operate at symbol signal-to-noise ratios (Es/No) as low as -5dB. A brass-board all-digital bit synchronizer with very low (0.05dB) degradation relative to an idealized analog model has been designed to process the 216 KBPS Manchester data symbols. This all-digital bit synchronizer, which provides soft decision detected outputs to a convolutional decoder, may be operated at any rate below 216 KBPS by merely changing the master clock frequency.

A Comparison of the Cesium and Hydrogen Hyperfine Frequencies by Means of Loran-C and Portable Clocks

Abstract: A comparison of the hydrogen and cesium hyperfine frequencies is made using a hydrogen maser calibrated directly against the Flexible Bulb Large Storage Box Hydrogen Maser and a Hewlett-Packard portable high performance cesium clock calibrated indirectly against the USNO Master Clock via a Loran-C link. The portable cesium clock is transported from the USNO to Harvard University in operating condition. This allows the evaluation of the portable clock's performance under transport. Data are presented on the epoch and frequency stability of the portable clock under transport as well as the usefulness of a closure measurement in determining clock drift.

Satellite Broadcasting of WWV Signals

Abstract: An experiment concerning the broadcasting of time and frequency information from geostationary satellites is discussed. Included are discussions on satellite motion, time delay, Doppler shift, and delay calculations. Ground station requirements, time recovery techniques, and timing resolution and accuracy are also included. Delay computation aids for the user were designed to provide free space delays between the master clock and the user. Measurements made in North and South America demonstrated a timing resolution of about 10 ?s and an accuracy of 25 ?s.

Slaving calculator chips

Abstract: An electronic calculator or data processing system implemented on semi-conductor chips to operate several chips in synchronism where at least one element common to the operation of all chips is responsive to sequentially generated operating states. A master clock applies clock pulses to the clock input terminal of one chip. A control gate is provided in the circuit leading to the clock input terminals of the other chip or chips. A comparator is connected to selected operating state output terminals from both or all of said chips and is connected to the control gate for inhibiting flow of clock signals to the other chip or chips so long as said selected states differ.

We Re-Set the Clock

Abstract: For twenty-seven years the clock of the Bulletin of the Atomic Scientists has symbolized the threat of nuclear doomsday hovering over mankind. The minute hand, never far from midnight, has advanced and retreated with the ebb and flow of international power politics, registering basic changes in the level of the continuing danger in which people have lived since the dawn of the nuclear age. Two years ago the minute hand was pulled back to 12 minutes to midnight as a consequence of the signing of the first arms control agreements which emerged from the Strategic Arms Limitation Talks between the United States and Soviet Union. This was an event which seemed to usher in a new era of sanity in superpower nuclear arms policies. In recognition that our hopes for an awakening of sanity were premature and that the danger of nuclear doomsday is measurably greater today than it was in 1972, we now move the clock forward to 9 minutes to midnight. We do not thereby venture a prediction as to when, or even whether, a nuclear holocaust may come, or to imply that the likelihood of its occurrence can somehow be closely calibrated. We offer instead an assessment and a warning. Our assessment is that in these past two years, and in particular these past few months, the international nuclear arms race has gathered momentum and is now more than ever beyond control. Our warning is that so long as control continues to

Performance of Loran-C chains relative to UTC

Abstract: The long term performance of the eight Loran-C chains in terms of the Coordinated Universal Time (UTC) of the U.S. Naval Observatory (USNO) and the use of the Loran-C navigation system to maintain the user's clock to a UTC scale, are examined. The atomic time (AT) scale and the UTC of several national laboratories and observatories relative to the international atomic time (TAI) are presented. In addition, typical performance of several NASA tracking station clocks, relative to the USNO master clock, is also presented. Recent revision of the Coordinated Universal Time (UTC) by the International Radio Consultative Committee (CCIR) is given in an appendix.

Circuit arrangement with automatic starting and amplitude stabilization, especially for small electronic clocks and watches

Abstract: A circuit arrangement, especially for small electronic clocks and electronic watches, which provides for automatic starting of the oscillator of the watch or clock upon energization of the circuit and which provides for amplitude stabilizing during the operation of the watch or clock.

A Design Basis for Ferro-Resonant Parallel Inverters with Silicon Controlled Rectifiers

Abstract: The paper describes the operation and design basis of medium power S. C. R. parallel inverter in which magnetic ferro-resonance has been utilised to achieve some desirable properties. Example of a specific system which consists of a 500 VA parallel inverter providing 220V, 50 Hz a.c. from a 48 volts d.c. input using ferro-resonant transformer and a constant frequency trigger circuit with crystal control and associated transistorised scale-down circuit has been discussed. The main advantages of such an inverter are economy in components and cost, inherent output voltage stabilization within ± 10% for variation in the input d.c. voltage as well as load changes, short circuit/overload protection, sinewave output with harmonic distortion less than 5% without using any additional filter and frequency stabilization accuracy of about 0.5 parts per million. The applications of such an inverter are in standby a.c. power supply for computers, frequency stabilizer/master clock control system for electric clocks, a.c...