Audio transmitter concealed in a cigarette packet, X-ray. The cigarettes are seen in the top half of the packet. They have been cut in half to provide room for the transmitter hidden underneath. The metal components are bright areas. The microphone (upper left) is connected to a circuit board that is seen across bottom. Above the circuit board is a switch (small rectangle), with a battery (large rectangle) to provide power. The coiled wire (at right) is the antenna for transmitting sound as radio waves to a receiver. This equipment could be used for covert surveillance (spying).