SYSTEM INCLUDING MUTUALLY CHANGEABLE SYSTEM PARTS AND THE SYSTEM PART

PROBLEM TO BE SOLVED: To obtain a user-friendly system by receiving a change request signal to request change of coupling between a first system part and another terminal, detecting the change request signal and establishing only a coupling first, other coupling at the second time and only other coupling at the third time respectively by at least one of the first and third system parts. SOLUTION: When a set up signal including a first address code to define a first address for a terminal 2 is detected, a memory means 61 is checked by a detecting/deciding means 15. For example, the first address code is stored in a first column, for example, and a second address code to define a second address for a terminal 4 is stored in a second column in a table of the memory means 61. In response to it, a coupling/removing means 11 is controlled via connection 52 so that the set up signal is transmitted to a receiving/transmitting means 13 as well, for example, via connections 30, 43 by the detecting/deciding means 15.