Telephone call-charge display system - has knobs to set tariff rates and calculates charge from tariff rates and call duration

摘要

The call-charge display system has an evaluation circuit receiving the call metering pulses sent to the telephone set from the exchange. The evaluation circuit calculates the cost of the telephone call from the tariff rate and the call's duration. The calculated cost is displayed. The tariff rates can be entered in the evaluation circuit using controls knobs. The system does not require direct wiring to the telephone set. The evaluation circuit reconstructs the dialled telephone number from the noise pulse generated during dialling.