FIELD: communication equipment. SUBSTANCE: in its bit error rate checking mode, device provides allocation of first channel CHO as frame synchronization channel, seventeenth channel CH16 as packet data transmission channel, and thirty second channel CH31 bit error rate checking. In bit error rate checking mode, trunk line is tested by means of bit error rate checking. In mode with blocked bit error rate checking, device reallocates seventeenth channel CH16 for its use as inter-frame synchronization channel. EFFECT: possibility of packet data transmission upon testing trunk line. 9 cl, 10 dwg
