Viking Range VGIC305-4BS - why is my old Viking range beeping? even when unplugged

I was trying to trouble shoot the wiring and power supply on my ancient Viking gas range VGIC305-4BS.
even with the power disconnected, the unit is beeping periodically.
why is that?

via Viking Range VGIC305-4BS - why is my old Viking range beeping? even when unplugged
by pjstock