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 it’s 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 subscriber’s 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.