In homes, small power transformers step mains voltage down to safer low voltages for devices like doorbells, thermostats, HVAC controls, and low-voltage lighting. They provide isolation from mains, reducing shock risk and allowing use of smaller gauge wiring on the secondary. Many modern devices integrate transformer and power-supply electronics in plug-in adapters. In panel-mounted applications, these transformers are often Class 2, limiting power so that faults cannot easily cause fire or severe electric shock.