Apparently Supertone Electronic Co. was a maker of motherboards, assuming it's the same Supertone Electronic Co. that made this.
I was hoping I could find their Chinese name by searching for their English one, but no luck. Far too blurry for me to make out what the components of the second character are!
Edit: And of course, taizou beat me to it, and got the Chinese name while he was at it.
Edit again: For once, the Chinese name actually makes sense given the English one. 巨=giant, 聲=sound. Giant sound = super tone.