This document discusses the design and use of mobile phone jammers. It outlines key parameters for jammer design such as frequency bands, distance to be jammed, and jamming-to-signal ratio. It provides block diagrams of components including power supply, IF section, and RF section. Potential applications of jammers are also discussed, such as maintaining silence in libraries, lecture halls, and hospitals. Legal issues surrounding jammer use are addressed for different countries. Future technologies that could control phones without actively jamming signals are also mentioned.