PURPOSE: To continuously transmit the incoming signals in an emergency for generation of ringer tones and to inform a called subscriber of an incoming call by adding a 2nd switch means in parallel to a 1st switch means which cuts off the ringer tones and turning on the 2nd switch means in the case the incoming signals are continuously received more than the prescribed frequency.

CONSTITUTION: A capacitor 4 is charged via a resistance 3 in a signal period and discharged via resistances 13 and 15 in a pause period. The charging time constant of the capacitor 4 is set shorter than the discharging time constant. Thus the charging voltage of the capacitor 4 rises up gradually as a whole even though the capacitor 4 is discharged in a pause period. If the incoming signals are continuously received in the specific frequence, i.e., 20 times, a transistor TR 5 is turned on. Then a TR 6 is turned on. Thus the ringer signal sent from a ringer signal generating circuit 11 is transmitted to a speaker 7 via the TR 6. Then the ringer tones are produced. As a result, the ringer tones can be produced in the case the incoming signals are continuously received in the fixed frequency.