| 摘要 |
<p>A method of switching synchronous signal sources of a synchronous data communication network having offices (A, B, C and D) connected to each other through circuits and synchronous signal sources installed inside and outside an office, in which even when a failure occurs in one of synchronizing signal sources, data communications are possible through switching the synchronizing signal sources to others according to the degree of the failure. Preset are flag bit data (S, *S), which indicate whether the synchronizing signal transmitted via the main wire is usable or not, in the signal including the synchronizing signal. When a failure occurs in one of the synchronizing signal sources, referring to the table specifying the priority order for selecting one synchronizing signal source, the table which is provided before-hand in every office, one synchronizing signal source is selected for every office according to the flag bit data. Then, in every office, the synchronizing signal source which has been selected at the present time is switched to a synchronizing signal source determined as mentioned above.</p> |
