PURPOSE: To simply check a terminal equipment identifier of each terminal equipment in a short time by using a terminal equipment identifier confirming procedure specified by the CCITT recommendations I.441 and an echo bit specified by the CCITT recommendations I.430.

CONSTITUTION: The terminal equipment identifier readout device 9 is connected to ISDN basic access subscriber's buses 7, 8 similarly to the two sets of ISDN basic access terminal equipments 5, 6. Then the terminal equipment identifier confirming procedure specified by the CCITT recommendations I.441 and the echo bit specified by the CCITT recommendations I.430 are utilized. Thus, the terminal equipment identifier used by the ISDN basic access terminal equipments 5, 6 of one set or over in existence with a link of the layer 1 set already is read and displayed automatically without manual check of each terminal equipment 5 or 6.