TESTING METHOD FOR SUBSCRIBER CIRCUIT

PURPOSE:To simplify a test system and a test procedure by testing a subscriber circuit by the testing device in the subscriber circuit based on the control information from the down side of a fourwire side highway, and outputting a monitor signal to the up side of the four-wire side highway. CONSTITUTION:A state setting circuit 10 sends an instruction for operating switches SW2-SW4 with a state setting signal inputted from the down side 13 of the four-wire side highway. The respective switches SW2-SW3 are switched to set the path of a ROM 7, a D/A converting circuit 8, an A/D converting circuit 6, and a digital level decision circuit 5 in order, and the decision circuit 5 checks whether or not pattern corresponding to a signal of specific frequency and level read out of the ROM 7 is transmitted correctly by the D/A converting circuit 8 and A/D converting circuit 6. consequently, the normalcy of the A/D converting circuit 6 and D/A converting circuit 8 is checked and the result is outputted to the up side 12 of the four-wire side highway through a monitor signal generating circuit 4 and an OR gate 11. Consequently, the test system and test procedure of the subscriber circuit are simplified.