Transformer 220V 12-0-12V (600mA)

Width is 50mm (75mm with mounting tabs)
Height is 40mm
Depth is 40mm

Input is 110V/220V. Output is 12V + 12V.
You get 24V by using the two blue wires.
If you need 12V you can use one blue and one black wire.

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.