Network communication system with an alignment signal to allow a controller to provide messages to nodes and transmission of the messages over four independent frequencies

摘要

A communication system with at least one controller and a plurality of nodes provides a procedure to enable the controller to connect and send messages to individual nodes to establish and maintain a communication link. The controller further receives an indication from the node when termination of receipt of a message from the controller by the node has occurred. The controller transmits connection information to a node to establish a communication path over which the controller can transmit a message to the node when the controller has information to send. A communication message can be sent by the controller, for example, when a node wanders into its control area to enable a communication link to be established.