not in use, this saves a lot of electricity. But most of the time the users forget to completely switch off these appliances, the given project is designed with this in mind, the circuit will indicate after every minute when the mains switch of an appliance is left open. The circuit will produce sound indication after every minute or after a preset time period to indicate the appliance switch is left open. The best feature of the circuit is that it will not require any physical connections with the appliance wire, just place its antenna near the wire and it will do the rest. 

How to use
After building the circuit connect the supply with the circuit the supply can be two 3V lithium coin cells. The current consumption of the circuit is only 650uA therefore the batteries will last longer. For best results use small antenna wire and place it near the appliance electric 220V AC cable. The circuit is quite sensitive the sensitivity can be adjusted with the 1M variable resistor connected between pin 2 and ground of the LM358 IC. The timing of the circuit can be adjusted with the 1M variable resistor connected between pin6 and pin7 of IC2.

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Electronic appliances for example computers, printers, air conditioners, Televisions etc. use electricity when they are in use but they still use some electricity when they are not in use, most of the electronic appliances contains power off switches but they still use some power when they are switched off, therefore it is always better to completely switch off an electronic appliance from mains supply when they are
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Electronic Appliance Switch Left Open Indicator Circuit Diagram