A request to access the network sent by a terminal is intercepted and a selective restriction criterion is evaluated on the basis of parameters relating to the intercepted access request. A radio signal is sent to jam an acknowledgment signal sent by the network in response to the access request if the selective restriction criterion is satisfied.

In a stand-alone device arranged to transmit messages to mobile communication devices, the massages are transmitted without affecting the normal communication in the mobile communication networks. The system can be located at any suitable location where mobile telephone communication is not desired. The system is arranged to transfer a predefined message in form of text or voice to the mobile communications device. This is obtained in that the system is designed to detect and force the mobile to lock on to a control channel of the system. Thereafter the system transmits a predefined text or voice message to the mobile telephony device users within the coverage area of the system. An application area is to prevent mobile telephony device users to have the device switched on in radiosensitive areas such as hospitals and aeroplanes. The device could also suitably be located in libraries, churches and theatres where ring signals and conversation is of disturbing nature.

The disclosed invention makes mobile terminals physically impossible to use in specific spaces without using radio waves of so high intensity as to affect medical devices and without requiring telephone companies that operate wireless communications systems (WCS) to take special measures. Cooperation of a telephone company on the implementation of making mobile terminals physically impossible to use in specific spaces makes mobile terminals provided by the telephone company easy to use. Pseudo signals of downlink pilot signal in WCS are emitted off the pilot timing in specific spaces. Uplink channel radio waves in cooperative telephone compannies' WCS are relayed and communication path is disconnected if the uplink channel radio waves are for communication of an attribute banned in the space. Communication path can be disconnected without increasing the intensity of radio waves so high. In cooperative telephone compannies' WCS, only the path of communication of an attribute banned in the space is disconnected.

The test results found that the EMI impact depended on the UWB power that fell within the receiver passband. Specifically, EMI occurred when the average power in the receiver passband was approximately equal to the desired signal level of the receiver. One waveform, TW7, did not cause EMI because the average power was too low. Three waveforms, TW1, TW2, and TW6 only caused EMI when the receiver was tuned to the frequency of the UWB spectral component. Three waveforms, TW3, TW4, and TW5, caused EMI at all receiver frequencies. As noted, these tests were performed to determine the susceptibility of various RF receiver (radars and communications systems) devices to UWB signals. The tests were not intended to evaluate the use of UWB signals for jamming purposes.

An ultra wideband (UWB) jamming system comprises a processor, a memory, a pulse generator, one or more UWB transmitters, and one or more UWB antennas. In an exemplary embodiment of the present invention, the RF signals of a threat transmission or an RF-triggered explosive device (RTED) are evaluated and a set of interference parameters defined for the RF signal of that device. The interference parameters are predetermined to interfere with the reception or transmission of the RF signal. The interference parameters are sent to a pulse generator that drives one or more UWB transmitters to generate a signal has a statistically high probability of jamming or introducing an error in the threatening transmission.