Brand new 24V 3A 3000 mA center tap AC transformer.
Input is 110V/220V.  Output is 12V + 12V.
You get 24V by using the two green wires.
If you need 12V you can use one green and one black wire.
With the mounting tab it measures W 95mm D 55mm H 50mm.
Without the tab it is W 60mm.

This is an AC transformer and the output is AC also.
If you need DC you need a power supply not a transformer.
If you try to measure the output using the DC setting in your meter it would not give you a voltage.
You need to set it to AC in order to measure the output voltage.

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