24/7 monitoring with up to 32 radios. With internal batteries, the system can run a few days without any power input but battery life may vary depending on conditions. AC system's use a AC power supply that plugs into a 110 outlet. Dc system's use a DC power from a solar panel without the need for a outlet. Note: additional radios can be purchase separately but each system is limited to a max of 32 radios.