CS 200 is a set that has been studied to inhibit telephonic traffic within a limited area. CS 200 is effective both against analog networks and GSM / DCS digital ones operating in the 900 MHZ and in the 1800 MHZ frequency. CS 200 works according to the principle of coherent interference through a constant density spectrum generator, with the aim to shield communication signals. In this condition mobile phone terminals behave as if there were no signals coming from plants that are in the territory. A virtual field absence is created and in this condition mobile phones do not receive or transmit until communication is restored. In order to create the signal CS 200 uses low noise oscillators that are controlled by PLL circuit, with quartz reference. Through a specific protection set, the energy transmitted is immediately blocked in case of anomalies in the control circuit of the generated frequency. These characteristics allow CS 200 to be effective only on cellular phone terminals, without producing any type of interference on any other communication radio set. Standard telephones, cordless telephones, PCs, medical devices, video systems, interphone and microphone systems are not disturbed by CS 200. In order to limit in the best possible way the area of action CS 200 has a regulator that allows to measure out precisely the emitted energy. CS 200 has coaxial connectors for the connection of the respective aerials, so that it is possible to use different types to adapt better to the various types of installation. Inshield has any type of aerial: omnidirectional, directional or environment low impact ones. Shielding areas IThe shielding area of CS 200 is function of some variables, as for example the position in which it has been put and the level of field of the mobile phone service. It is obvious that the farther the mobile phone plant is located, the wider the area covered by CS 200 is. In an average situation in which the display of the telephone shows a level of field of 70% ( about 3 on 5) the covered area is approximately 200 – 300 m2 , in case the indication is 5 on 5 the area can be reduced to about 50 m2 , while with a lower than 3 on 5 level areas of more than 1000 m2 can be inhibited. The above mentioned values are considered using unitary power omnidirectional aerials, in case higher power aerials are used , the shielding area can increase.