Every person wants security from an unknown person in the absence specially when children are at home. Two Way Communication Security System For Household is the specially designed circuit for such type of security. The circuit is built around infrared transmitter and receiver and intercom circuit. When any object interrupts, the infrared signal transmitted by infrared transmitter the infrared sensor in receiver circuit detects this and energizes the relay connected at the output section of the infrared receiver. As relay is, energized melody generator circuit starts generating the melody sound. Thus people inside the house gets alert that someone is at your gate. Now for your security you can start communication with that unknown person. The arrangement of speaker and microphone are such that you can easily communicate with the person outside your house. Thus you are secured from an unknown person.  
About the Circuit : The circuit is built around infrared transmitter and receiver, melody generator circuit and two way communication circuit as shown in the circuit diagram.
Transmitter circuit :  
Two Way Communication Security System For Household consists of a timer IC as IC1 connected as an astable multi vibrator, driving an output transistor, which switches the IR LED D1, ON, & OFF. The duration of the transmitted light pulses is about 10ms and the repetition rate is just less than 1 KHz. The sensitivity is adjusted by adjusting preset P1.
The power supply for the transmitter is not critical provided the output voltage is not greater than 9V as this could result in the maximum current rating of D1.
Receiver Circuit :
Receiver section comprises power supply an infrared detector module, time delay circuit with noise filter, bistable flip-flop and an output section. The infrared sensor is used for sensing the IR signal from the transmitter section. In normal operation i.e. without any interruption output at pin2 of IR sensor are high, T2 remains OFF. IC4 is not triggered. When any object interrupts the IR beam falling on sensor, pin2 goes low. Transistor T2 turns ON. Consequently, capacitor C5 starts charging through resistor R9. When voltage across capacitor C5 reaches about 3.5V, pin2 of IC4 receives a high pulse. As IC4 is two input EX-OR Gate, output at pin 3 goes high. Transistor T3 conducts and low pulse is applied to trigger pin2 of IC5. IC5 being operated in monostable mode gets triggered. Output at pin3 of IC5 goes high and relay is energized. LED D2 glows which gives visual indication. Pin 3 remains high for a time set by R12/P2/C9. This time delay is set by preset P2. The NO (Normally Open) output of relay is given to melody generator circuit, which receives supply through relay. The melody sound is heard till relay is ON. Thus,  the unknown person is detected through melody sound. When ON signal is available output of sensor goes high and T2 is switched OFF. Now capacitor C5 starts discharging through R8 and voltage across it decreases to zero. When another signal arrives capacitor, C5 again charges through R9 and IC4 gets triggered again. IC3 is a regulator IC that provides a regulated voltage.
Now the communication starts. The communication circuit is built around amplifier IC as IC6 and tone generator is designed using astable multivibrator IC7. As there is a two-way communication, two sets are designed. Sound signals generated due to communication are received by condenser MIC connected at audio input pin2 of IC6/IC8. These signals are amplified by audio amplifier and the amplified output generated at pin6 is given to transistor T5 and T6. The signal is again amplified and the final output is given to speaker. There is also a volume control that, can be set with the help of preset P3/P4. Switches S1 and S2 are used to start the communication. When S1 is, pressed IC7 gets triggered and oscillations start. These oscillations acts as tone input to IC6.

Every person wants security from an unknown person in the absence specially when children are at home. Two Way Communication Security System For Household is the specially designed circuit for such type of security. The circuit is built around infrared transmitter and receiver and intercom circuit. When any object interrupts, the infrared signal transmitted by infrared transmitter the infrared sensor in receiver circuit detects this and energizes the relay connected at the output section of the infrared receiver. As relay is, energized melody generator circuit starts generating the melody sound. Thus people inside the house gets alert that someone is at your gate. Now for your security you can start communication with that unknown person. The arrangement of speaker and microphone are such that you can easily communicate with the person outside your house. Thus you are secured from an unknown person.  
About the Circuit : The circuit is built around infrared transmitter and receiver, melody generator circuit and two way communication circuit as shown in the circuit diagram.
Transmitter circuit :  
Two Way Communication Security System For Household consists of a timer IC as IC1 connected as an astable multi vibrator, driving an output transistor, which switches the IR LED D1, ON, & OFF. The duration of the transmitted light pulses is about 10ms and the repetition rate is just less than 1 KHz. The sensitivity is adjusted by adjusting preset P1.
The power supply for the transmitter is not critical provided the output voltage is not greater than 9V as this could result in the maximum current rating of D1.
Receiver Circuit :
Receiver section comprises power supply an infrared detector module, time delay circuit with noise filter, bistable flip-flop and an output section. The infrared sensor is used for sensing the IR signal from the transmitter section. In normal operation i.e. without any interruption output at pin2 of IR sensor are high, T2 remains OFF. IC4 is not triggered. When any object interrupts the IR beam falling on sensor, pin2 goes low. Transistor T2 turns ON. Consequently, capacitor C5 starts charging through resistor R9. When voltage across capacitor C5 reaches about 3.5V, pin2 of IC4 receives a high pulse. As IC4 is two input EX-OR Gate, output at pin 3 goes high. Transistor T3 conducts and low pulse is applied to trigger pin2 of IC5. IC5 being operated in monostable mode gets triggered. Output at pin3 of IC5 goes high and relay is energized. LED D2 glows which gives visual indication. Pin 3 remains high for a time set by R12/P2/C9. This time delay is set by preset P2. The NO (Normally Open) output of relay is given to melody generator circuit, which receives supply through relay. The melody sound is heard till relay is ON. Thus,  the unknown person is detected through melody sound. When ON signal is available output of sensor goes high and T2 is switched OFF. Now capacitor C5 starts discharging through R8 and voltage across it decreases to zero. When another signal arrives capacitor, C5 again charges through R9 and IC4 gets triggered again. IC3 is a regulator IC that provides a regulated voltage.
Now the communication starts. The communication circuit is built around amplifier IC as IC6 and tone generator is designed using astable multivibrator IC7. As there is a two-way communication, two sets are designed. Sound signals generated due to communication are received by condenser MIC connected at audio input pin2 of IC6/IC8. These signals are amplified by audio amplifier and the amplified output generated at pin6 is given to transistor T5 and T6. The signal is again amplified and the final output is given to speaker. There is also a volume control that, can be set with the help of preset P3/P4. Switches S1 and S2 are used to start the communication. When S1 is, pressed IC7 gets triggered and oscillations start. These oscillations acts as tone input to IC6.