Risco GT-480 Strobe stays on?

Hi
I recently moved house, and there's ageneric alarm fitted. I've tracked it down as a Risco, the control panel is a GT-480.
The external box leds flash, and the strobe flashes too. I've armed and reset, and the code I have must be a manager code because it lets me into the settings, but I can't find a way to turn the strobe off.
I'd be more than happy to just disconnect the whole thing to be honest - but I can't see how to power it all off.