PURPOSE: To enhance the controllability for the attendant board through omission the same numbers of the higher-rank groups in the continuous call extension numbers by adding newly the higher-rank digit number display unit of the subscriber number plus the display number information transfer part to the attendant board of the private telephone exchange.

CONSTITUTION: The attendant board consists of central control unit 1, the lamp/ display signal control circuit and display circuit 2, BLF control and display circuit 3, attendant board key circuit 4 and subscriber selection key circuit 5 each. Furthermore, extension number extractor 22, higher rank digit group display circuit 21 and key signal transmission timing control circuit 23 are added newly. In such constitution, the operation from the higher-rank digit can be omitted if the higher- rank digits are in the same group when a subscriber selects another subscriber. As a result, the controllability can be enhanced, and at the same time the device can be miniaturized.