Abstract: A detector for detecting telephone-activated devices, such as cellular telephones used for remotely triggering explosive devices, includes a transmitter for generating and transmitting a pseudo base station signal corresponding to a base station for a telephone-activated device, and a receiver for receiving and detecting a response signal transmitted by the telephone-activated device. At least part of the transmitter and at least of the receiver may be located within a shield of conductive material, such as a cone-shaped metal shield, that aids in localizing and directing the transmitting of the pseudo base station signal toward an object to be interrogated (with regard to whether or not it contains a telephone-activated device in an idle state). The detector has a response unit for providing a response when a telephone-activated device is detected, such as providing an alarm to an operator or interdicting operation of the telephone-activated device.