Panel fit and supply voltage
The Omron K8AB-VS1-24VAC is a voltage monitoring relay that runs on a 24 VAC supply. It's a current-production part, so it's still a standard line item for new panels and replacement stock.
What it monitors and where it goes
This relay monitors voltage levels on a 24 VAC control circuit. It sits in a panel, typically on a DIN rail, watching for undervoltage or overvoltage conditions that could drop out contactors or damage downstream electronics.