PURPOSE: To easily remove terminals, by putting terminals judged as under a nonmounting condition, terminals whose circuit is blocked and which have a relationship, and circuits into a vacant condition in electronic swichboards.

CONSTITUTION: Central control equipment 1 judges that a line substrate controlling circuit 6 and a trunk substrate controlling circuit 13 are under a nonmounting condition when they do not give any response to the enquiry about the mounting, and performs releasing operations on line circuits 7 and 9, line controlling circuits 8 and 10, and terminals 17 and 18 which are to be mounted on a print substrate 5. Because of such operations, the same condition as the initial condition can be obtained at any time during the course of exchanging operation. The central control equipment 1 automatically blocks terminals after performing this operation, and thus terminals are easily removed.