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I have a data sheet that gives the coil pickup voltage as "0.85…1.1 x Us] and coil dropout voltage as "0.3…0.6 x Us".
I am assuming that Us refers to the nominal or specified coil voltage, but why is it "Us"?
Subscript S in \$U_S\$ symbol stands for German word die Spule which means the coil. So \$U_S\$ is the coil voltage.
Required, but never shown