PURPOSE: To reduce the burden of the operator and to prevent the misdialing of the operator for an exchange adopting the absence transfer, by displaying dialed numbers, in dialing of the operator of an attendant board.

CONSTITUTION: After the reception of an incoming call by an attendant board from a main trunk CBWT, an extension number of a called extension SUB-A for a requested connection is dialed. This dial information is transmitted to a central controller CCU via a position unit (POSU) and the absence transfer of the extension SUB-A is recognized via a memory (not shown). Thus, a ringing trunk RGT is connected with the called extension SUB-B to call out the SUB-B, and a number reception unit NDPU reads out the connected number and dial number information counted and stored, and the extension number of the extension SUB-B being the connected number and of the dialed SUB-A is respectively displayed on the number display of the attendant board and the dial number display.