PURPOSE: To simplify the constitution of a measuring circuit and to quickly execute highly accurate measurement by inputting a digital test signal to a decoder and measuring a test signal level by a digital signal outputted from a coder.
CONSTITUTION: A digital test signal generating means 1 samples a test signal, generates a digital test signal similar to a digital signal converted by a coder and sends the test signal to a decoder in a subscriber's interface board. A test signal returning means 2 returns the signal generated from the means 1 and converted into an analog signal by the decoder to the coder included in the subscriber's interface hoard. A digital test signal measuring means 3 measures a test signal level based upon the digital signal converted by the coder to output the test signal.
UESHIMA TAKESHI
TANAKA KAZUO
NISHIOKA GOJI
