Telephonic communications – With usage measurement – Call charge metering or monitoring
Patent
1991-10-09
1992-12-15
Schreyer, Stafford D.
Telephonic communications
With usage measurement
Call charge metering or monitoring
379251, 379322, H04M 1500, H04M 1538, H04M 1900
Patent
active
051724073
ABSTRACT:
A circuit (4) for generating metering pulses (P) includes a multiplier circuit (MULT), a bandpass filter (BF), a comparison circuit (COMP) and a ramp signal generator (RAMP). A current (IC) from the ramp signal generator is multiplied (MULT) by an alternating voltage (VTXX) such as to form the metering pulse (P), which is transmitted, together with a speech signal (SP), to a subscriber (1) for registration. The output voltage (UF) of the bandpass filter (BF) is compared with a reference voltage (UR) in the comparison circuit (COMP). The output (9a) of the comparison circuit is electrically conductive only when the filter voltage (UF) exceeds the reference voltage (UR). When control signals (D) open a switch (SW), a capacitor (C1) is charged by a first current generator (10). The capacitor voltage (VC) incresases linearly and controls proportionally the current (IC) of the ramp signal generator (RAMP). When the filter voltage (UF) reaches the reference voltage (UR), the voltage (VC) of the capacitor (C1) is held constant. This is effected by small charging and discharging of the capacitor (C1) for each period of the alternating voltage (VTTX) when the output (9a) of the comparison circuit shifts between non-conductive and conductive states. When the current switch (SW) is closed (D), the capacitor (C1) is discharged by a current 2.times.IS) through a second current generator (11) until the metering pulse (P) ceases.
REFERENCES:
patent: 4638122 (1987-01-01), Siligoni et al.
patent: 4720852 (1988-01-01), Siligoni et al.
patent: 4829517 (1989-05-01), Malek
Patent Abstract of Japan, vol. 13, nr. 207 (E-89), abstract of JP 1-025660, published 27 Jan. 1989, NEC Corp.
Schreyer Stafford D.
Telefonaktiebolaget L M Ericsson
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