Pre set off timer automatically turns off the devices after set time. Many of us have habit to fell asleep while watching TV or while listening music and the device [[wysiwyg_imageupload::]]remains switched on for the whole night. For such problems, you can use this simple circuit which will turn off the device automatically after the set time and will also engage an alarm. You can also vary the set time according to your requirement. This can also be used by students who are preparing for competitive exams they can use it as alarm clock. This simple circuit is built around four transistors. Connect the power supply and press the push to on switch momentarily to on the device. Keep on reading to find out how this circuit is assembled and how it works.