Abstract: A method for providing and for testing adaptive echo cancellation in an apparatus including transmission equipment for data communication. The apparatus includes a 2-wire to 4-wire hybrid circuit which receives a signal from a remote end which is cut off for purposes of the testing method. A signal consisting of randomly occurring ones and zeros is applied to the send end of the apparatus. Also included in the apparatus is an adaptive echo canceller which cooperates with the send end and with a filtered signal received from the hybrid circuit to produce a correction signal which is fed back to the adaptive echo canceller and which is also compared with threshold values for purposes of testing the function of the apparatus.

Abstract: A method and apparatus in a telecommunication system for activating from idling state to active state. This system includes a digital transmission link consisting of a subscriber side containing a subscriber terminal (NT) and a station side containing a line terminal (LT) assigned to the station, the line terminal being connected to a clock pulse oscillator (CLM) constituting the master clock for the system, and the network terminal being connected to a local clock pulse oscillator (CLS) constituting a slave clock. Activation may take place either from the subscriber side or from the station side. In activation from the subscriber side an activation request signal (AR) is sent from a subscriber to the network terminal (NT) from which a cyclic bit pattern is sent to the line terminal (LT). The bit pattern is detected and sent as an activation request to the station which sends an activation order (AO) back to the line terminal.