Design and Construction of an Audio Surveillance System

Abstract

Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people and events for the purpose of influencing, managing, directing, or protecting them. In this paper, an audio surveillance system was designed, simulated and constructed by replacing discrete components with an integrated circuit(CD2003) with the view of taking advantage of electret microphone ability to capture sound of low frequency and transmit it to the receiver where the signal can be retrieved. The audio signal was then amplified using two bipolar junction transistors (BJT), modulated and transmitted via an antenna. A provision for recording of the retrieved signal was made using a telephone set for continual logs of information for retrieval purposes at the receiver section. The circuit was designed and fully implemented with a designed output power of 0.3watts which transmitted within 8-12meters radius and waveforms from proteus 8 professional and multism software were obtained and compared for performance and evaluation. This short range of coverage was designed and implemented with the aim of avoiding major interference from the surrounding since the system is meant to survey a small area like banking hall, bulk cash rooms and other sensitive areas.