I just faced "UC input" while reading a Relay's catalogue. In the catalogue it has been told that the relay can have DC input,UC input and AC input. so what is UC input? I searched for it but didn't find anything useful.

  • 2
    \$\begingroup\$ Can you provide a link to whatever it was that used "UC Input?" \$\endgroup\$
    – JRE
    Commented Oct 31, 2016 at 11:03
  • \$\begingroup\$ Just googled this up and found it here: Input UC, 24V UC, etc.. \$\endgroup\$
    – Wesley Lee
    Commented Oct 31, 2016 at 11:09

1 Answer 1


Standard a relay is designed for VAC or VDC input only. In the case that the relay input is designed for VUC both kinds of supply are allowed. In other words. It is safe to supply the relay with VDC or VAC. The letter U stands for universal. A little rectifier is build in the relay to make this possible. The danger of burned relays because of using an VAC relay when a VDC relay is required is gone that way.

  • \$\begingroup\$ so if the catalogue says that the relay can have 48 V UC as input, it means that both 48 V AC and 48 V DC inputs are possible? \$\endgroup\$ Commented Oct 31, 2016 at 11:17
  • \$\begingroup\$ That is correct. The advantage is that the user no longer has to find out what is needed \$\endgroup\$
    – Decapod
    Commented Oct 31, 2016 at 11:17

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