Suppose you have an heater in a room and you want that the heater should be made on or off based on from a remote location and heater on/OFF can be made
The methodology described here can be used is applicable for any remote device activation and deactivation.Now consider a security scenario suppose you have to record some of the activities of your room (as you are not at home and want to record activities within the room )This can also be achieved by remote activation using device switching mechanism using telephone line.So what you need to have a working landline to implement this method.
This method has many other advantages also,just think you can control almost any electronic device from the remote location by just making a simple call to your home.Another situation:say when you left the home you just forgot that whether you have switched off all your light ,fans etc.
Now if you have this mechanism available to you from remote location where ever you are if you can mange a telephone line to call to your phone you can make the lights and fans off just like any electrical device you can do.
So this way any device can me made on/OFF based on telephone line and remote switching.This kind of remote switching can be achieved by the use of DTMF decoder IC,The task of DTMF decoder IC is to decode the DTMF tones coming from remote phone which are used to activate the devices in the home. So at room the DTMF decoder is placed and the decoder then after decoding the DTMF signals(which are coming through the telephone lines form remote end(say you are at the remote end are pressing the switches/telephone keys))Then the decoded signal is used to activate the relay(DC relay/Ac realy depending on what kind of device you want to activate).So this is the concept of this project.