TELEPHONE SET

PURPOSE: To manage a speech charge accurately by informing the occurrence of abnormality upon the detection of the occurrence of the abnormality in a speech charge management equipment so as to allow its recovery and to prevent trunk line call data and trunk line termination call data from being aborted. CONSTITUTION: When a connection flag '01H' is set to a speech charge management equipment connection flag memory section and a central processing unit 9 receives an ACK, a normal flag '00H' is set to the speech charge management equipment connection flag memory section to instruct turning-off of an alarm lamp, and when the processing unit 9 receives a NAK, an abnormal flag '01H' is set to control the turning-on the alarm lamp. When no idle area is available in the storage area of a memory 10 in the case of a trunk line call, the call is in holding. When the abnormal flag '01H' is set, synthesized voice data representing disable trunk line call are read from a voice synthesis circuit 17 and the data are sent to extension telephone sets 2a to 2n having made a call.