PURPOSE: To reduce a circuit scale by using a pseudo pattern generating/ confirming circuit for simultaneous communication of plural channels to decrease the test time due to the preparation of test or the like, and transmitting the pattern among plural channels.

CONSTITUTION: In the case of applying communication test for transmission and reception between a terminal side equipment 11 and a transmission line side equipment 11, contacts of a 1st switch 13 and a 2nd switch 14 are connected to the position (b) to send a 1st cycle 511th pseudo pattern of 9-bit constitution at terminals D0-D8 of a 1st RAM 3 to the transmission line side equipment 11 via the 1st switch 13. A pseudo pattern confirming section 6 inputs the 1st cycle 511th pseudo pattern inputted via the 2nd switch 14 to a comparator 9 and a channel address of 5-bit constitution from a control memory 1 is inputted to the 2nd RAM 7 and compared with a read pseudo data and the result is sent. Similarly, the readout/write is repeated between the 2nd RAM 7 and a 2nd pseudo pattern generating circuit 8.