The SMS Tank Alert is fitted to your oil tank & sends the oil level direct to your Smart phone. Details can be sent on a daily/weekly or monthly basis. - Low level & high level messages sent automatically. - Can be used on oil tanks 0.5m-3m in height or diameter. - Sudden high usage assumes theft condition & will automatically send a SMS text message to your smart phone. - Powered by 4 batteries. Alarms when they need replacing. - Sim card pin unlocked required & not supplied.