PURPOSE: To perform emergent communication to a subscriber during absence, by making the operation with the specified conditons when a caller informed of the absence of a called party, and the called party connectable, if an incoming call comes to the subscriber telephone set which has finished automatic answering telephone registration with the automatic answering telephone function.

CONSTITUTION: When a subscriber B dials a secret number NA, a CPUCC references a secrent number PC from the received number NA and a number of a subscriber A in call information stored in a main storage device MM and picks up the secrent number NA stored corresponding to the subscriber A number and compares the number with a dialed secret number NA of the subscriber B. When both the secret numbers NA are coincident, the CPUCC connects the subscriber A to a callout signal trunk RGT to call out the subscriber A and makes connection change for the subscriber B from a register trunk RT to a callout tone trunk RBT and returns the callout tone. When the subscriber A responds, the CPUCC connects the subscribers A and B to make emergency call possible.