System for monitoring the radioelectrical performance of mobile telephony networks including base stations controllers connected through digital data transmission lines (13, 14) to base transmitting stations, wherein the system comprises electronic devices specifically fitted to read data transmitted onto said lines, and to process said data to calculate and correlate specific operating parameters of telephony networks and to create tables of statistics of network operating events, said devices being further connected to central processing units to which they periodically transmit said pre-processed data for later searching and processing activities characterized in the electronic devices being non-intrusively connected to the transmission lines (13,14), wherein said specific electronic devices comprise: - sections (16,17) dedicated to amplification of electric signals transmitted on said lines and to extraction of digital data from said signals; - sections dedicated to analyse the structure of said data and to divide them into synchronised packages; - sections dedicated to decode the transmission protocol of each data package, and to detect and extract the message associated to the package and its parameters; - section dedicated to creation, for each type of extracted message, of tables of events corresponding to each data package parameters, wherein the section is arranged to perform the following: - after creating the table, each of its cells is arranged to detect exactly a specific operating event composed by combination of the values of its row parameter and column parameter, - when in one of the data packages the type of message corresponding to the above table is found, one of the cells of the table can be detected by using the values of the package whose parameters define that table as values of row and column, - the number memorised in that cell is increased by one unit, to mean that the detected event has occurred once again in the mobile telephony network under analysis, and - that cell automatically shows the number of times of occurrence of the event during a specific time gap, that is, it is a statistical counter of that event; and - section dedicated to send all the above data tables onto external processing unit. - sections (16,17) dedicated to amplification of electric signals transmitted on said lines and to extraction of digital data from said signals; - sections dedicated to analyse the structure of said data and to divide them into synchronised packages; - sections dedicated to decode the transmission protocol of each data package, and to detect and extract the message associated to the package and its parameters; - section dedicated to creation, for each type of extracted message, of tables of events corresponding to each data package parameters, wherein the section is arranged to perform the following: - after creating the table, each of its cells is arranged to detect exactly a specific operating event composed by combination of the values of its row parameter and column parameter, - when in one of the data packages the type of message corresponding to the above table is found, one of the cells of the table can be detected by using the values of the package whose parameters define that table as values of row and column, - the number memorised in that cell is increased by one unit, to mean that the detected event has occurred once again in the mobile telephony network under analysis, and - that cell automatically shows the number of times of occurrence of the event during a specific time gap, that is, it is a statistical counter of that event; and - after creating the table, each of its cells is arranged to detect exactly a specific operating event composed by combination of the values of its row parameter and column parameter, - when in one of the data packages the type of message corresponding to the above table is found, one of the cells of the table can be detected by using the values of the package whose parameters define that table as values of row and column, - the number memorised in that cell is increased by one unit, to mean that the detected event has occurred once again in the mobile telephony network under analysis, and - that cell automatically shows the number of times of occurrence of the event during a specific time gap, that is, it is a statistical counter of that event; and - section dedicated to send all the above data tables onto external processing unit.