METHOD AND APPARATUS FOR AUTOMATIC CHARGE CALCULATION

摘要

PURPOSE:To automatically calculate communication charge at subscriber side without direct contact with telephone lines, by detecting a leakage magnetic field at a magnetism detector fitted to a telephone set cord and discriminating a dial signal according to the change in DC current flowing to the telephone set. CONSTITUTION:A magnetism detector 3 is fitted to a cord 2 of a telephone set 1 with a clip and detects a leakage magnetic field. Based on the detection of this leakage magnetic field, the change in a DC current flowing to the telephone set 1 is detected at a detection and discriminating circuit 4. A telephone number and a call period signal detected and discriminated at this circuit 4 are applied to a processing circuit 5, where unit charge information stored in a storage circuit 6 is read out for a specified operation and the result is applied to a display 7 and a printer 8. Without direct contact with telephone lines, the call charge can automatically be calculated and recorded at a subscriber.