PURPOSE: To transfer a message smoothly by periodically calling an extension subscriber to be informed of the message and by allowing it to hear the message from a message transmitter when the extension subscriber answers.

CONSTITUTION: Information on an extension subscriber to be informed of a message, when inputted from a switchboard through an input equipment INPUT, is stored in a storage device MM. At prescribed time, a controller CONT calls an extension subscriber A, stored in the device MM, through a message transmitter MSG. In this case, if the subscriber A makes no answer within certain time, the calling is interrupted. At the next prescribed time, it is called again and when the subscriber A answers, the device MSG is connected to the subscriber A, and he is informed of the message. After the subscriber A hears the message and returns its handset, the information on the extension subscriber is erased from the device MM and from the point of the next prescribed time, the extension subscriber is not called.