PURPOSE: To prevent the forgetting of a message and an erroneous message by transmitting a message at busy to ask the registration of the message to a caller whom a call incomes in busy, waiting the finishing talking of a busy extension telephone, automatic-calling the applying extension telephone and notifying the message of the caller with being registered.

CONSTITUTION: When a call incomes from the subscriber of an extension telephone 3 to an extension telephone 1 while the subscriber of the extension telephone 1 talks with an extension telephone 2, a central processor 9 connects the extension telephone 3 and a voice storage device 7 through a main switch and notifies the subscriber number of the extension telephone 1 to the voice storage device 7. The voice storage device 7 reads a busy message registered by the subscriber of the extension telephone 1 previously and notifies it to the subscriber of the extension telephone 3. The subscriber of the extension telephone 3 registers the message to the subscriber of the extension telephone 1 to the voice storage device 7 and finishes talking. When the extension telephone 1 finishes talking, the voice storage device 7 calls the extension telephone 1, and transmits the message registered by the subscriber of the extension telephone 3 previously and transfer processing is completed.