What is the difference between a selv and a selv and a pelv circuit?

A SELV (Separated Extra-Low Voltage) circuit operates at a maximum voltage of 50V AC or 120V DC, designed to minimize the risk of electric shock. A PELV (Protected Extra-Low Voltage) circuit also operates at similar voltage levels but includes additional protective measures, such as insulation or barriers, to ensure safety. The main difference lies in the added safety features of PELV systems, which can help prevent accidental contact with higher voltages.