Killjoy circuit
A Killjoy Circuit is the (semi-humourous) name given to any device which creates interference with, degrades, or destroys annoying electronic equipment, including mobile phones, hi-fi systems, car stereos, and the like. It comes from a Gary Numan song titled "The Joy Circuit".
A typical Killjoy Circuit might include a high-grade power supply, amplifiers, capacitors, and a spark gap or solenoid / electromagnet to create the requisite EMF interference. Many devices which can be used as ad hoc Killjoy Circuits already exist, such as Tesla coils, old (pre-2000) cellular telephones, CB sets and nuclear weapons. The only mass-produced devices specifically designed to destroy, degrade or interfere with electronic equipment, however, are the E-bomb and the TV-B-Gone universal remote control, and thus they can also be considered to be Killjoy Circuits.