PURPOSE: To use a public line from an optional non-protocol terminal equipment immediately after a line interrupt request from the non-protocol terminal equipment by releasing the connection between a communication processing unit and a public line with a line interrupt request from the non-protocol terminal equipment connecting to the public line.

CONSTITUTION: This system is provided with a transmission means 121 in a communication processing unit 12 sending a text to a non-protocol terminal equipment 15 connecting to a public line 14 from a job program 111 in a host computer system 11, a reception means 122 in the communication processing unit 12 receiving a text from the non-protocol terminal equipment 15 connecting to the public line 14 to the host computer system 11 and a line interrupt means 123 in the communication processing unit 12 interrupting the line by a line interrupt command from the non-protocol terminal equipment 15. The line is available of use immediately by releasing the connection between the communication processing unit 12 and the public line 14 with the line interrupt request from the non-protocol terminal equipment 15 in this way thereby improving the line efficiency.