other attributes This device monitor controlles a 3- other phase net for correct phase attributes sequences and total failure of the phases. It operates according to the closed-circuit current principle and hence monitors itself. Therefore, it is guaranteed that in case of a malfunction of the system it will shut down save. If all phases are in the right position the output relay puts through, the contact 11-14 is closed. In case of incorrect phase or phase failure the relay drops out. The contact 11-12 is closed. Even a faulty fuse is recognized as a phase failure, if no voltage is fed back to the measuring relay by the user. The pick-up time in the case of an incorrect phase position is 70 ms, the drop-out time 40 ms. The air gaps and leakage paths of the test circuit were sized according to the VDE 0110C, 550 V AC, those of the output circuit designed according to VDE 0110C, 250 V AC.