Fujitsu Corporation

Tatsuru Iwaoka

Masato Kobayashi

Takashi Nakajima

Akio Morimoto

Kazumaro Takaiwa

Akio Takayasu

Hideaki Koyano

Kazunori Kawabe

Yasushi Yoshino

Minoru Tateno

A clock supply device includes a receiving unit configured to receive frame synchronization packets from an asynchronous network and generate timing signals; a phase comparing unit configured to perform phase comparison by comparing phases of the timing signals generated by the receiving unit and clock signals generated by an internal oscillating unit; a phase variation detection unit configured to detect a frequency variation of the frame synchronization packets based on a trend of a variation amount of a phase difference that is obtained by performing a statistical process on count values obtained as a result of the phase comparison; and an oscillating frequency control unit configured to control an oscillating frequency of the internal oscillating unit when the phase variation detection unit detects the frequency variation of the frame synchronization packets.

Clock supply device and transmission device

A redundant changeover apparatus causing no frame synchronization loss even upon occurrence of changeover between working system and protection system. In case of an in-apparatus synchronization system, when two input signals which are mutually asynchronous in phase are changed over by a changeover switch, a changeover switch, a clock extractor, a PLL circuit, and a clock changing portion transmit signals with clocks before the changeover being gradually changed to clocks after the changeover. Alternatively, in case of an in-apparatus synchronize system, data are separated from clocks so that the data are once changed to data with reference clocks, and then for the data, clocks before the changeover are gradually changed to clocks after the changeover.

Redundant changeover apparatus

Growing community of inventors

Kawasaki, Japan

Tatsuru Iwaoka