PURPOSE: To transmit an alarm if a line is connected erroneously by comparing the contents of a transmission control memory or a reception control memory with the contents of a line collation memory through the comparison of an identification code added thereto respectively.
CONSTITUTION: To a sub-burst transmitted respectively from N-set of transforming circuits TR, the 1st identification code specific to the transforming circuits is added. In synthesizing the bursts, multiplex separation control circuits CONT are provided with the 2nd identification code specific to each multiplex circuit in addition to a transmission control memory and a reception control memory, separate the 1st and 2nd identification codes corresponding to each received sub- burst, compare the contents of the line collation memory and transmit an alarm when they are not coincident.
MITANI TOSHIHIKO
HAYASHIZAKI HIROKI
MOROTOMI HITOSHI
NIPPON TELEGRAPH & TELEPHONE