Transformer Center Tap 110/220VAC to 18V AC 9V-0-9V AC, 1000mA (1A),

Center Tap AC TransformerInput AC Voltage: 120V / 240VOutput AC Voltage: 18V or 9V + 9V.Current: 1000mA 1A max Wire Leads: 100% copper, 6.5" long
Width: 50mm (74mm with tab)Depth: 37mmHeight: 42mmNet Weight: 10 oz 
Primary:

• For 110V AC input, use one of the Red and the Black wire. 
• Insulate and DO NOT connect the other Red wire, since it will be Hot when you power the other Red wire. (DO NOT connect both Red wires together, or you will create a short circuit and damage the transformer!)
• For 220V AC input: use two Red wires. DO NOT connect the black wire.

Secondary:

• For 9V AC Output: use one blue and black wire (DO NOT connect the 2 blue wires together or you will create a short circuit and damage the transformer!)
• For 18V AC Output: use two blue wires

If you need DC voltage then you need a power supply not a transformer.If you try to measure the output using the DC setting in your multimeter, it will not give you a voltage.You need to set it to VAC in order to measure the output voltage.