2. OVERVIEW OF PROPOSED APPROACH
Interactive voice response refers to technology supporting the interaction of
customer with the service provider generally over the telephone lines.
When a person wants to access any of the services of the Interactive Voice
Response System, he presses a number through his telephone keypad.
The pressed number appears across the line and the ring detector circuit senses this
ring.
After a specified number of rings the relay is activated through the microcontroller,
which in turn connects the line to DTMF decoder.
The activation of relay causes the number pressed to appear across the DTMF
decoder.
The decoder decodes the number pressed and then the decoder output is passed
through the microcontroller to the computer.
Now, when the caller presses a number, the number pressed is decoded by the
DTMF decoder and passed to the computer through the microcontroller.
The computer recognizes the number and accesses the particular file from the
database to output the voice message.
The output voice is passed through the voice card where the digitized serial data is
converted into analog voice form and passed to the line.
The caller gets the information through the line.
3. REQUIREMENTS
HARDWARE REQUIREMENTS
o Basic Microcontroller based Hardware
• To interface Telephone line
• To provide various control signals
Give commands serially to PC
o Telephone Line Interfacing Circuit
• Ring Detection Circuit
o DTMF Decoder Circuit
• To detect DTMF Pulses on telephone line
o USART Serial Port Driver
• For serial communication between
microcontroller and laptop
SOFTWARE REQUIREMENTS
• Net Beans 6.9
• Arduino Interfacing software
• Proteus V7.6
4. COMPONENT DESCRIPTION
DTMF DECODER 8870
The DTMF (Dual Tone Multi Frequency) decoder is a specific IC which performs the function of
converting the DTMF frequency tones into BCD codes.
These BCD codes are fed to the microcontroller to process the data and take necessary action.
DTMF decoder 8870 IC has an external crystal oscillator to generate the clock signal, the pins
to detect the presence of DTMF tone at its inputs and pins to transmit the BCD codes to the
microcontroller.
These frequencies are compared with the Vref at the IN+ pin. This comparator pin output is then
filtered and fed to the digital detection algorithm within the IC.
It then passes to the code converter where it is converted into 4 BCD codes.
Its features are:-
• Complete DTMF Receiver
• Low power consumption
• Internal gain setting amplifier
• Adjustable guard time
• Central office quality
• Power-down mode
6. MICROCONTROLLER ATMEGA328
Following task are done by microcontroller in our hardware:
1. As power is switched on microcontroller is reset and sets the Mode and the baud rate required
for serial communication with PC.
2. Monitors ring detector circuit. When ring detector circuit gives low signal to μC it picks up the
phone by applying high signal to ON/OFF hook simulator.
3. Microcontroller now informs the PC that call has been made by sending character ‘1’ to the PC
to activate IVRS software. Now μC checks the StD pin status of DTMF decoder.
4. When StD is at logic high level means that a number has been registered. So microcontroller
reads it, and transmits that number hex to PC through TxD pin (serial communication).
5. Whenever the user press hash key (#) on telephone pad, then call is to be terminated or if user
does not press any number for 70 sec then also call is to be terminated.
6. Microcontroller sends a low signal to ON/OFF hook switch simulator to terminate the call.
8. SERIAL COMMUNICATION INTERFACE
The main purpose of the RS 232 IC is
• To act as a serial interface between the microcontroller and the PC.
• It provides the voltage compatibility between the TxD and RxD pins of the
microcontroller and the serial port of the PC.
• The voltage level of the TxD and RxD pins of the serial port of the PC are 12V.
• The R S 232 IC therefore provides compatibility required to interface the computer and
the microcontroller.
11. • Thereafter using this PCB was made.
• In order to communicate between system and microcontroller, a serial port driver board is
used.
• The code for detection of the BUTTON pressed is written in Arduino IDE and burnt.
• Thereafter the DTMF Decoder is connected to the Microcontroller.
• Finally a battery is connected and complete system is made functional.