PURPOSE: To indicate and control various line tests by a line testing device itself, by providing a line leading-in device and by leading in a designated line to be tested to the line testing device and controlling it.

CONSTITUTION: When the test operator depresses a line leading-in designating button 14 after executing various set operations, designated information is read through a line designating switch 12 by a line testing device 1, and this read information is sent to a level converter 4 of an exchange 3 through a leading-in designating line 2. In the exchange 3, a relay driving device 7 is controlled by a central control device 6 in accordance with read information, and the driving device 7 controls a line leading-in device 9 through a leading-in control line 8. Contacts rl0∼rln corresponding to a designated line are operated in respective relays RL0∼RLn in the line leading-in device 9, and the designated line is led into the line testing devicd 1. The line testing device 1 tests the line.