interval on communication lines 801 through 805 each status representation is shown as an elongated rectangle connected to its associated communication line by a free hand line each segment of the status representations includes a channel designation e g ch3 and the use being made of that particular channel a dash under the channel designation indicates that the channel is unused the term cm followed by a number indicates that the data words for a communication having a given numerical designation are being conveyed in the associated channel the numerical designation of the communication is arbitrary but it has the property that a given communication must retain the same designation throughout the duration of the communication and that the same designation cannot apply to two different communications at the same time for example channel 3 ch3 on communication line 801 is being used to convey data words which form communication 2 cm2 from node 100 to node 101 as shown by status representation 106 by the previously described method of channel selection channel 3 on communication line 808 is being used to convey data words which form communication 2 from communication node 101 to communication node 100 the following is an example of the establishment of communication between an origination node 101 and a destination node 103 communication node 101 generates a request for communication with communication node 103 and transmits that request via a data path 503 to loop controller 800 in response to the request for.