Patent ID: 7420924

Claim:
A transmission system which comprises a transmitting terminal station, a receiving terminal station, a relay station and a transmission line for connecting them, said transmitting terminal station, comprising: a selection/output unit for selecting and outputting either a regular signal or a test signal to be transmitted to the receiving terminal station; a setting control unit for setting the transmission device to either a normal mode or a standby mode; a signal detection unit for detecting whether there is a signal from an external input line of the transmitting terminal station; and a selection/output control unit for enabling the selection/output unit to select and output a test signal when the transmission device is in the standby mode and when there is no signal from the external input line of the transmitting terminal station, wherein said transmission device prevents the transmitting terminal station, the receiving terminal station and the relay station from issuing an alarm by transmitting a test signal instead of the signal to be transmitted if no signal to be transmitted is not transmitted yet although a line setting of the transmission device is completed.