Abstract: The process to measure the signal quality of a digital information transmission system using a scanning device with adjustable direct current threshold can determine a signal parameter for the signal quality (Q-factor), which can determine the bit-rate from an unknown input signal and with its help a clock signal can be generated to scan the input signal with the scanning device. The device includes a detection device as well as a clock generator, which is connected to the detection device and receives a pre-adjustment signal, and which synchronizes with the input signal over a phase locked loop with the scanning device through phase comparison. Process and device allow the monitoring of systems in a shortest time and facilitate statements concerning the bit-rate of the respective line section as well as concerning the size of the Q-factor and all relating variables.