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Page 5



1. Project Overview ~ Integrated Telephone Data Logging (ITDL) System


ITDL consists of six main components. Namely,


1.      DTMF receiver

2.      Polarity reversal circuit

3.      Real Time Clock (RTC)

4.      Memory devices

5.      Printer driver

6.      RS232 driver



The fig.1 depicts the basic block diagram of the system. The DTMF block, forming a temporary storing device encodes the telephone number dialed by subscriber while polarity reversal circuit checks two party (calling party and called party) call establishment. At the moment of call establishment, the Real Time Clock (RTC) interprets itís current Binary Coded Decimal (BCD) value to a register of Z80 together with call hang up time to the next register for the computation of the call duration. At the end of this process, the telephone numbers dialed, the call-originated time and the call duration are stored at consecutive memory locations for later retrieval. At the end of each month, subscriber can connect printer to the port which makes an interface to the RAM to print a detailed listing of the subscriberís monthly telephone calls.  An RS232 driver and port are incorporated into the system to access the system software through computer terminal and especially for future expansions. Therefore, the complete system replicates a standard microprocessor based control system.
















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Last modified: July 13, 2002