METHOD OF SYNCHRONIZATION STATUS MESSAGE PROCESSING IN TRANSMISSION APPARATUS
 Inventors: Seiji Meki; Shunji Yamada, both of Kanagawa; Junichi Moriyama,
Kawasaki, all of Japan
 Assignee: Fujitsu Limited, Kanagawa, Japan
 Appl. No.: 09/022,429
 Filed: Feb. 12, 1998
 Foreign Application Priority Data
Jan. 9, 1997 [JP] Japan 9-235759
 Int. CI.7 H04J 3/06
 U.S. C I 370/512
 Field of Search 370/438, 439,
370/503, 509, 510, 512; 375/354, 356
 References Cited
U.S. PATENT DOCUMENTS
FOREIGN PATENT DOCUMENTS
6125354 5/1994 Japan .
Primary Examiner—Ricky Ngo
Attorney, Agent, or Firm—Helfgott & Karas, PC.
A transmission apparatus has units to which main signals are input for subjecting these main signals to predetermined processing and then transmitting them. One of these units is a master unit and the others are slave units and they are interconnected by a clock cable and processor-to-processor cable. Each slave unit detects a synchronization status message that has been inserted into a main signal input from a line and notifies the main unit of this synchronization status message via the processor-to-processor cable. Using synchronization status messages acquired from the slave units and a synchronization status message that has been inserted into a main signal input thereto, the main unit obtains the synchronization status message indicative of the best quality level and adopts, as a master clock, a clock extracted from the main signal into which this synchronization status message has been inserted.
12 Claims, 18 Drawing Sheets