Monitoring of cost of telephone call - uses interconnection unit between line and electronic calculator with print:out facility

摘要

A small electronic calculator with a print out is used with an interconnexion unit to display data such as telephone number called and the cost. Call charges can be observed during the call period. An interconnecting unit between a telephone line and a calculator comprises a receiving unit (401) which detects the pulses of the numbers dialled and also the cost pulses. The number pulses are processed (301) and applied to a sequence unit (302) to print the output of a charge calculator sequencing circuit (402). Interface circuits (303) ensure matching between these circuits and the calculator.