A Voice Time Monitoring and Recording Sub-System for the Telephone Speaking Clock

Previous research has developed a time source selecting and data monitoring system (TSMS) for the time synchronized speaking clock (TSSC) [1]. This developed includes two sub-systems. One is for multi-time signal source selecting and the other is for input status monitoring. In this research, the TSMS was extended to monitor the output of the TSSC on dedicated telephone line, called TSMS_A1. From this sub-system, an interrupt circuit with a Linux kernel driver was developed for capturing the rising edge of the on-time tone which is from TSSC output to produce an interrupt event. Through this event, the TSMS’ controller was trigged immediately to measure the time error and record the announced voice program into an audio file. The audio recording procedures and a raw file converting from PCM (Pulse Code Modulation) into Waveform Audio File Format (WAVE) were studied. In the system design, Unified Modeling Language (UML) notation tools, such as user case diagram and activity diagram were used to express basic concepts of the system requirements and interactive behaviors. Finally, the data were analyzed from the on-time tone measured by setting three typical threshold levels. Comparing these results, optimum one was chosen as the input threshold for the TSMS_A1. Its time comparison error is within ±100µs after the path delay has been removed. From this result, we could indeed monitor the output status of the TSSC and then could be providing more reliable voice time service for users.