SYSTEM FOR ACCOUNTING TIME OF TELEPHONE CALLS Russian patent published in 1998 - IPC

FIELD: communication equipment, in particular, limitation of time of telephone calls and charging for time over this limit using established rate. SUBSTANCE: device has user call counter 1, phone set 2, which is connected to automatic phone exchange 4 through user line 3. User call counter 1 has interface unit 5, first digit detector 10, tone signal analyzer 11, control unit 12, power supply 13, oscillator 14, frequency divider 15, total call time counter 17 and indicator 18. Goal of invention is achieved by introduced first, second and third gates 7, 8, 9, inter-series pauses detector 6, read-only memory unit 16. Automatic phone exchange 4 has receiver 19, commutation set 21 and computer 22. Goal of invention is achieved by introduced control and protection unit 20 which has first and second electronic gates 23, 24, inter-series pauses detector 25, inter-series pauses counter 26, RS flip-flop 27, shift register 28 for receiving protection number, comparison circuit 29 and read-only memory unit 30. EFFECT: increased quality of communication between user call counter and automatic phone exchange. 2 cl, 4 dwg