How to identify regulated adapters?

Question

First of all, I would like to replace the six aa batteries in my lego NXT robot with an ac adaptor with 9V of output. I know that I need to have a regulated adapter to prevent the voltage from going up if the load is lower than the supplied amperage (it doesn't use that much).

How do I identify a regulated adapter without using a multimeter? Can I assume that an adapter meant for a piece of electronics is good? What about universal adapters?

Does a line with a dotted line underneath connecting the volts to amperage under output on adapter mean it is regulated?

Something like:

Output 5.0V ======== 550ma

but with a dotted lower line

I wonder if that might be a sign just because I have seen that double line only on adapters that I assume are regulated because they power electronics, but it could be completely coincidental and not a proof.

Answer 1

Unregulated adapters are usually small and inexpensive.  A regulated adapter, or power supply, will cost a little more but won't break the bank.  Just ask for a regulated 9 volt power supply and you'll get what you need.