Abstract 

This work involves the design and development of a digital signal detector which is capable of detecting incoming and outgoing signals from mobile phones. The presence of an activated mobile phone can be detected by this handy, pocket-size mobile signal detector from a distance of one and a half meters, which could be used in preventing the use of mobile phones in examination halls, classrooms, confidential rooms etc. The circuit can detect the incoming and outgoing calls, text messages, and video transmission even if the mobile is kept in the silent mode. The moment the gadget detects Radio Frequency (RF) transmission signal from an activated mobile phone, it starts sounding a beep alarm and the Light Emitting Diode (LED) blinks. The alarm continues until the signal transmission ceases. The circuit is assembled on a general purpose PCB as compact as possible.  The completed design circuit is analyzed using a multsm software, oscilloscope and multimeter to measure the output voltages across various components when there is or no signal. The results obtained shows how efficient this device can serve the purpose of which it was designed. Officials from West African Examination Council (WAEC) will benefit from the study, since it has been their ambition to stop examination malpractices in Ghana. The study will add up knowledge, both theoretical and practical aspect of electrical and electronic students.