초록 ▼

A method and apparatus are provided for maintaining and correcting a time reference in a satellite controlled digital clock system. A time code message including time-of-year information and satellite position information is transmitted in a data stream from a transmitter on earth to a satellite orb

A method and apparatus are provided for maintaining and correcting a time reference in a satellite controlled digital clock system. A time code message including time-of-year information and satellite position information is transmitted in a data stream from a transmitter on earth to a satellite orbiting the earth to be relayed back to receivers located around the world. The data is transmitted at a precise data rate. According to the invention, a local clock oscillator is phase locked with the precise data rate, thereby providing the clock system with time-of-year information by counting the pulses produced by the local oscillator. At the same time, the digital clock system assembles the time code message from the received data stream and compares the message with the time accumulated by counting the pulses produced by the oscillator. After a predetermined number of errors are detected by such comparisons, the clock system resets itself to coincide with the received time code message. If transmission of the time code message is interrupted, the clock continues counting pulses produced by the local oscillator and thereby continues keeping time undisturbed. In a preferred embodiment, the digital clock system is implemented with a firmware programmed micro-computer and the time-of-year and satellite position information is displayed on light emitting diode digital displays.

대표청구항 ▼

A digital clock system in which a data stream is transmitted at a precise data rate, the data stream comprising a plurality of contiguous data records, each data record comprising a plurality of data blocks, each of said blocks having a data synchronization segment and a message code segment, the me

A digital clock system in which a data stream is transmitted at a precise data rate, the data stream comprising a plurality of contiguous data records, each data record comprising a plurality of data blocks, each of said blocks having a data synchronization segment and a message code segment, the message code segments within a data record forming a time code message and said message including a message synchronization portion and a time-of-year portion, said clock system comprising: receiver means for receiving the transmitted data stream; a clock means for generating clock pulses at regular intervals; phase lock loop means for phase locking said clock means to the precise data rate of said data stream; and logic means for detecting the data synchronization segment of a data block so as to determine the position of each following message code segment in the received data stream, for detecting the message synchronization portion of the time code message so as to determine the beginning of the time code message, for assemblying the complete time code message from the individual received message code segments, for keeping time by counting said clock pulses, for comparing each complete time code message with the time represented by said counted clock pulses so as to provide a determination of whether said time coincides with the complete time code message, and for correcting the time represented by said counted clock pulses so that said time coincides with the complete time code message, responsive to a predetermined Number of determinations of non-coincidence between said time and said complete time code message.