The SQ 0214 is a microprocessor-based synchronising unit. It is intended for a phase difference measurement between a bus bar and generator. It can be used in any kind of installation where a manual or semi-automatic synchronising is required. Circular set of 24 LEDs represents a phase difference. SQ 0214 has LCD backlight display for a display of a generator UGEN and bus-bar UBB voltage and both frequencies fGEN and fBB or D j . It replaces two voltmeters and two frequency-meters, which are normally part of the synchronising set. A synchronising condition is set, when the phase difference and the voltage difference between UGEN and UBB, for a time of delay, are within the set limits. The synchronising check relay is then switched on and a SYNC LED is lit for a preset pulse time (e.g. 100ms, 300ms).