Network synchronization control system and control method

A method of controlling the synchronous exchange of information between a local network having a plurality of nodes and an external network, comprising the steps of:

• receiving external network clock signal information from said external network by at least one of said plurality of nodes;
• detecting at each of said plurality of nodes the presence of external network clock signals received by way of said local network;
• selecting any one of said plurality of nodes to be a control node which issues inquiries to each of remaining ones of said plurality of nodes as to whether said clock signals are being received from said external network;
• correlating said external network clock signal information with said clock signals received by way of said local network to determine at each of said remaining ones of said plurality of nodes that said clock signals are being received from said external network;
• replying by said remaining ones of said plurality of nodes to said control node whether said clock signals are being received from said external network;
• selecting a transmission node by a command from said control node to one of said remaining ones of said plurality of nodes that is receiving said clock signals from said external network;
• and
• generating at said transmission node in response to said command said clock signals for all of said plurality of nodes based upon said external network clock signal information.

A network synchronization control system in a communication network which has a plurality of nodes connected to a transmission line to form a local network, and which is connected to an external network and synchronously exchanging information therewith, said network synchronization control system comprising:

• a) a clock signal receiver means in at least one of said plurality of nodes for receiving external clock signals from said external network, correlating said external clock signals with a clock signal pattern and upon detecting a match generating a status signal to indicate the occurrence of a normal external clock signal;
• b) a clock transmission controller means in said at least one of said plurality of nodes for generating local network clock signals and other data frame signals in response to said external clock signals received by said clock signal receiver means;
• and
• c) means in at least a remaining one of said plurality of nodes for activating said clock transmission controller means of said at least one of said plurality of nodes from which said status signal is received.

A network synchronization control system in a communication network having a plurality of nodes connected to a transmission line on which said plurality of nodes exchange communications in the form of data frames, and one or more of said plurality of nodes is connected to an external network, said network synchronization control system which comprises:

• a) clock signal detection means in each of said plurality of nodes for detecting external clock signals in said data frames received from said transmission line;
• b) clock signal receiver means in each of said one or more of said plurality of nodes for receiving said external clock signals from said external network, and generating a clock normal signal when said external clock signals are normal;
• c) clock transmission controller means in each of said one or more of said plurality of nodes for receiving said external clock signals from said clock signal receiver means and storing said external clock signals in one of said data frames upon receipt of a command signal in another one of said data frames received from said transmission line;
• c) channel controller means in each of said plurality of nodes responsive to said external clock signals received from said clock signal detection means for effecting a synchronous exchange of information with said external network;
• and
• e) means responsive to said clock normal signal in one of said plurality of nodes for issuing said command signal in said another one of said data frames to said clock transmission controller means of one of said plurality of nodes issuing said clock normal signal.