초록 ▼

Time referenced RF signals are periodically received and processed for updating a microprocessor-controlled clock. The clock automatically scans several frequencies at which the coded RF timing signals are transmitted, selecting the strongest received signal for synchronization therewith and causes

Time referenced RF signals are periodically received and processed for updating a microprocessor-controlled clock. The clock automatically scans several frequencies at which the coded RF timing signals are transmitted, selecting the strongest received signal for synchronization therewith and causes a capture LED to be illuminated upon detection of a sufficiently strong signal at the beginning of a minute tone at one of the received frequencies. The microprocessor periodically determines the timing difference between an internal timer and the received RF timing signals. A time difference correction is provided to a digital-to-analog converter which provides an appropriate voltage to a varactor diode in a crystal oscillator circuit for adjusting the microprocessor\s operating frequency until it can no longer resolve a difference between the received RF timing signals and its internal timer. This permits highly accurate clock operation in between the periodic reference time updates and eliminates cumulative time error. Manual switches are provided for correcting for received signal propagation delay and for selecting the appropriate time zone as well as for allowing for daylight saving time and UTC1 correction. In addition, the microprocessor-controlled crystal oscillator ensures accurate time-keeping when the transmitted RF timing signals are too weak for clear reception.

대표청구항 ▼

A clock responsive to time-based signals for keeping time in accordance therewith, said time-based signals including encoded timing information, said clock comprising: receiver means for receiving said time-based signals; decoder means coupled to said receiver means for processing said time-based si

A clock responsive to time-based signals for keeping time in accordance therewith, said time-based signals including encoded timing information, said clock comprising: receiver means for receiving said time-based signals; decoder means coupled to said receiver means for processing said time-based signals and deriving said timing information therefrom; control means responsive to a timing reference signal for controlling the operation of said clock in accordance therewith, said control means coupled to said decoder means and responsive to said timing information for comparing said timing information and said timing reference signal and generating a correction signal representing the time difference between said timing information and said timing reference signal; variable oscillator means coupled to said control means and responsive to said correction signal for adjusting said timing reference signal so as to coincide with said timing information and providing the thus adjusted timing reference signal to said control means in synchronizing said control means with said timing information, wherein said variable oscillator means comprises an oscillating network which includes a fixed frequency oscillator in combination with variable capacitance means coupled to said control means and responsive to said correction signal.