The device provides tracking of a generator's voltage and frequency to the mains, in order to switch it on in addition to the network at minimum difference and the same phase angle. This unit measures voltage and frequency of two AC power networks between 2 phases each. As soon as control over the control input has been released, the SYN-6 generates corresponding offset pulses for the generator voltage and frequency. If both values differ within the preset tolerances to the leading mains, the unit emits a synchronisation pulse. In order to compensate delays of the switching elements, the sync impulse is given prematurely by the lead time, prior to the calculated sync time. The voltages and frequencies are displayed during operation. In addition, LEDs indicate all input and output switching states. This also applies when monitoring the voltage and frequency deviations permissible for synchronisation. All tolerances and nominal values are adjustable via parameters.