Harmony Control. This monitoring relay is used to control and monitor pumps in single-phase and three-phase networks. In single-phase networks (230 VAC), monitoring for overcurrent and undercurrent is carried out using true RMS measurement and in three-phase networks (208-480 VAC) monitoring for phase sequence and phase failure is also carried out. The device can be used to control pumps for monitoring or for 2-point control of a fill level, for which the corresponding control inputs are available.