PURPOSE: To attain callback from a police station and a fire station after line restoration for a No110 and No119 call from an extension telephone set of an exchange by providing a function corresponding to the talking of No110 and No119 call to an office line trunk circuit according to program control in a private branch exchange of the stored program system.

CONSTITUTION: When an extension telephone set 1 makes a call, a specific dial detection connection means 80 discriminates whether a dial signal is for No110 or No119, a channel switch 5 uses a 1st connection route 11 to connect the No110 and No119 call to an office line trunk circuit 7 to start talking. When the talking is terminated, an extension number storage means 81 stores an extension telephone number of the telephone set 1 acquired by the circuit 7 to a main storage device 9 to start a timer means 82. When an automatic connection means 86 detects a callback from a police station or a fire station while the timer means 82 is in operation, the state of the telephone set of the extension telephone number stored in the device 9 is checked and higher priority is placed on the callback for the connection.