Electronic telephone monitoring unit
The project described in this thesis attempts to enhance telephone metering by providing the telephone user with detailed call information. The Kenyan telephone network is still largely analog. Its capability is therefore limited to capturing only some of the key call parameters. The unit developed in this work offers the customer more details. A unique aspect of this unit is that it is installable at the Subscriber's end office. In order to detect the line status precisely from the end office, it becomes necessary to transform the exchange voltage to TTL logic levels. In so doing, complete between electrical isolation must be maintained the telephone line and the intelligence circuitry. In this project, a system capable of accurately monitoring a telephone line and producing a desired output has been designed, built and tested. The Z80 microprocessor has been relied upon for data processing. The stored programme control (SPC) approach has been adopted to make the project more cost effective. Z80 assembler language has been used in this respect.