Abstract: Analyzer for monitoring the traffic of a group of trunks conveying decimal code signalling and dialling impulses and multifrequency code signalling and dialling signals. It comprises multifrequency signalling receivers in a number smaller than the trunks of the group which are connected to the trunks only during the time when the same convey multifrequency signals. As this time is variable according to the phase succession of the telephone call, means are provided for defining the last decimal code impulse before the beginning of multifrequency signalling which serves for connecting a multifrequency signalling receiver to the trunk and the last multifrequency code signal according to the call phase succession which serves for disconnecting the multifrequency signalling receiver from the trunk.