Relay K1 has a low-impedance coil and K2 has a high-impedance coil. When a sensor opens, current is routed throu
gh the coil of Kl. K1 activates, opens its contacts, and prevents a sensor contact reclosure from affecting the circuit. When Kl contacts open, current to the main relay K2 is limited by the impedance of Kl. 2 controls power to a load (air conditioner, furnace blower, etc.).