Showing papers on "Master clock published in 1972"

Means for synchronizing clocks in a time ordered communications system

Abstract: A time ordered communications system wherein a master station equipped with a master clock which includes a reference oscillator disseminates correct time to remote stations equipped with local clocks which include local oscillators by transmitting a synchronization signal whose time of arrival at the remote station with respect to an internal reference pulse generated by the remote station is a measure of remote station clock error. The time interval between receipt of the synchronization signal and generation of the internal reference pulse is digitally determined to produce an error signal which is used to add or delete local oscillator pulses so as to immediately phase correct the local clock. In addition, the first and second time derivatives of the error signal are obtained and used to compensate the local clock for oscillator drift and other errors.

A Programmable Digital Pulser for NMR

Abstract: A programmable digital pulser for pulsed NMR applications employing inexpensive integrated circuits is described. This pulser employs two types of modules, one master clock and several counters. The required pulse sequence determines the number of counters to be front‐panel interconnected. The master clock module simultaneously provides crystal‐controlled clock pulses with periods from 10−7 to 1 sec in decade steps. These pulses are used by the counter modules to generate either time delays or pulses with a maximum resolution of five digits.

System for measuring time differences between remote clocks and for synchronizing the same

Abstract: System for measuring the time difference between a master clock and a slave clock located respectively in two remote stations and synchronizing these clocks. It comprises, in the master clock station, a time base generator controlled by the master clock, a source of light, an electro-optical detector, control means depending upon the time base generator for switching on the light source and control means depending upon the electro-optical detector for switching off the light source. The slave clock station comprises a time base generator controlled by the slave clock, an electro-optical detector detecting light from the master clock station, a chronometer switched on by the time base generator and switched off by the electro-optical detector and another chronometer switched on and off respectively by the first and second output signal of the electro-optical detector. Means are provided in the slave clock station for partially receiving and partially reflecting the light to the electro-optical detector at the master clock station causing the light source to produce a luminous signal whose start and end are split by a duration equal to twice the light propagation round trip time between the two stations.

System for measuring time difference between and synchronizing precision clocks

Abstract: System for measuring the time difference between a master precision clock and a slave precision clock situated respectively in a master and a slave station remote from each other. The clocks generate timing pulses with respective frequencies very close to each other. The master station includes a laser source of light pulses generating luminous pulse signals, a local detector of these signals and means for transmitting them towards the slave station. The slave station includes a detector of the luminous pulse signals and means for reflecting the same towards said master station. Two chronometers in the master station measure the time difference between the instant of generation of a luminous pulse signal and a master clock timing pulse and the time difference between the instant of generation of a luminous pulse signal and the instant of detection of a reflected back luminous pulse signal and a third chronometer in the slave station measures the time difference between the instant of detection of a luminous pulse signal and a slave clock timing pulse.

Automated Timekeeping

Abstract: An automated data collection and processing system designed to maintain and control the U. S. Naval Observatory (USNO) master clock system is described. Phase difference and time interval measurements (better than 0.1-ns resolution and 1.0-ns precision) from an ensemble of atomic clocks are used to construct a master clock time scale with a stability of parts in 10-14 on a near real time basis. Physical realization and dissemination of the time scale is achieved through program-controlied subsystems. The control and automatic data processing (ADP) systems are discussed and an analysis of system performance is made.

Pcm telecommunication system with standby clock

Abstract: At a main terminal connected to a remote terminal by way of a PCM signal path, a master clock controls the multiplexing of incoming messages from local lines for transmission over an outgoing line of that path to the remote terminal in a bipolar code enabling extraction of the clock frequency at the remote terminal. A discriminator at the main terminal continuously checks the operation of the master clock and, if that operation is normal, causes the transmission of a verification bit over the outgoing line to the remote terminal in an assigned time slot of a service channel of a period message frame; at the remote terminal, a detector responds to either the absence of the verification bit or the nonarrival of message signals to activate a standby clock controlling the sending of composite messages to the main terminal over an incoming line of the signal path. An extractor at the main terminal, connected to that incoming line, delivers the reconstituted pulses of the standby clock to the multiplexer in lieu of the output of the master clock if the latter operates improperly or not at all, as determined by the associated discriminator; a similar discriminator at the remote terminal may insert a corresponding verification bit into a service slot of a message frame transmitted to the main terminal to establish the correct functioning of the standby clock.

Time synchronization via lunar radar

Abstract: The advent of round-trip radar measurements has permitted the determination of the ranges to the nearby planets with greater precision than was previously possible. When the distances to the planets are known with high precision, the propagation delay for electromagnetic waves reflected by the planets may be calculated and used to synchronize remotely located clocks. Details basic to the operation of a lunar radar indicate a capability for clock synchronization to ±20 µs. One of the design goals for this system was to achieve a simple semiautomatic receiver for remotely located tracking stations. The lunar radar system is in operational use for deep space tracking at Jet Propulsion Laboratory and synchronizes five world-wide tracking stations with a master clock at Goldstone, Calif. Computers are programmed to correct the Goldstone transmissions for transit time delay and Doppler shifts so as to be received on time at the tracking stations; this dictates that only one station can be synchronized at a given time period and that the moon must be simultaneously visible to both the transmitter and receiver for a minimum time of 10 min. Both advantages and limitations of the system are given. Finally, an experiment is described which has detected the effects of lunar topography and libration on radar results; a monthly cyclic effect in time synchronization of about ± 6 µs is shown.

Collision avoidance system ground station synchronization

Abstract: A collision avoidance system ground station has its clock phase synchronized with a master clock through the use of a line-of-sight radio link. Multiple two-way synchronization rangings are exchanged between the ground station and the master clock. A digital counter at the ground station obtains the average deviation of the ground station clock with respect to the master clock and applies this average deviation to calibrate or synchronize the ground station clock with the master clock. Subsequently, further multiple two-way synchronization rangings are exchanged between the ground station clock and the master clock. A digital counter at the master clock now obtains the average deviation of the master clock with respect to the ground station clock as a check of the validity of the ground station clock calibration.

Detection of cycle slippage between two signals

Abstract: Clocking signals are recovered from an incoming signal train by a master clock oscillator phase locked to the incoming signals, and, in the event of a failure or malfunction involving the master clock, by a standby clock similarly phase locked to the incoming signals. One of the malfunctions occurs when the phase of the clock output slips a cycle with respect to the phase of the signal train. It is determined that a cycle slippage condition exists when phase comparisons of the signals indicate the clock output is passing from a phase lag error to a phase lead error, or vice versa, without passing through a region of no phase error.

Setting mechanism for secondary clocks

Abstract: A master-secondary clock system in which a master clock having a high order of accuracy, acts to regulate the operation of a plurality of remotely disposed secondary clocks. This is accomplished by means of a direct-current control pulse which is transmitted to the secondary clocks from the master clock, and is received at each secondary clock by an electromagnetic setting mechanism adapted to reset the seconds hand of the secondary clock to bring it into registration with the seconds hand of the master clock. The setting mechanism is also adapted to shift the hour hand of the secondary clock one hour ahead or back, depending on whether a transfer is to be made from Standard to Daylight Savings time or vice versa, this action being effected concurrently with the resetting of the seconds hand, but only when the control pulse is transmitted during a predetermined interval in the course of the day, the direction of shift depending on the polarity of the control pulse.

Master clock standby switching circuitry

Abstract: A power system for a master clock motor or the like which includes automatic switching circuitry for enabling instant switch-over from main power operation to standby power operation in the event of a temporary main power loss.

Widely separated clocks with microsecond synchronization and independent distribution systems

Abstract: In a majority of timing applications, a problem exists in setting two or more clocks to agree with one another. Present techniques using WWV or other HF broadcasts allow clocks to be synchronized within 1 msec. This paper describes a method which offers an improvement in synchronization of three orders of magnitude. Microsecond synchronization is obtained by use of the Loran-C navigation system as the link between a master clock at Boulder, Colorado and any slaved clock anywhere in the Loran-C service area. The timing system also includes a unique method for distribution of several time code formats on a single UHF channel.

Clock synchronization circuit

Abstract: The receiver clock of an asynchronous half-duplex data link in a call concentrator is initiated and synchronized by a synchronization circuit which responds to level transitions in a received pulse train and overrides the internal operation of the receiver clock to pull it into synchronism with the transmitter clock each time a level transitions in the receiver clock is out of phase with the corresponding level transitions of the transmitter clock as embodied in the pulse train. The two clocks of the data link are identical and can function either as master or as slave, depending on the direction of transmission.