LINE TRACING SYSTEM

PURPOSE:To make the trouble inspection of a line scanning mechanism easy by selecting a specific line from plural lines independently of the line scanning mechanism without influences upon operations of mechanisms in a communication control processing device and tracing this selected line. CONSTITUTION:A communication control processing device (CCP) 10 is provided with a line tracing part (TRC) 20. A comparing circuit 23 compares the address of a desired specific line in an address register 22 with a line address signal CAD synchronously with a scan timing signal SCT, and the output is outputted to an AND circuit 24 in each bit position of data of the specific line. The circuit 24 sends the output as a timing signal to a character assembling circuit 26 when the output of the circuit 23 and a bit service signal BSVC are applied simultaneously. A multiplexer MPX25 data of transmission or reception, which is selected by a transmit signal XMiT, to the character assembling circuit 26. The circuit 26 takes in effective data of the specific line from reception data Di (or transmission data Do) of the MPX25 and assembles characters in accordance with line attributes and stores them in a control part 27. The line scanning mechanism (CS) is monitored on a basis of this data.