What is the "signal" line on this PSU?
I found your board http://www.hobbyic.com/products.php?product=Step-down-PSU-3.3v-5v-9v-12v. The regulator chip info is obfuscated and their documentation online is nil.
Usually these chips have a RUN input . But with 8 pins and 4 step down voltages, it wont handle too much power. (Note dont use on 1W video cam.)