That is a Manual ON/ OFF SINGLE battery switch. Not designed for more than one battery. It is usually installed to turn OFF all of the connected Battery loads(appliances/Circuits). But, depending on who installed it and the parameters from who installed it, it may NOT shut off all Battery loads. But, you need to leave the Disconnect ON at all times when using the RV. When stored with no 120 volts connected turn it off. THEN go inside and see if you find any 12 volt item still on. Some that may bypass the disconnect. Doug
1. CO detector
2. LP detector
3. TV antenna booster(very rare but does happen)