Vạn Tín has put together quite a surveillance package for a very reasonable price. It includes a DVR recorder for indoor use and four weatherproof outdoor cameras, too. The recorder supports up to eight channels and will automatically record over old footage, but only if you tell it to. The outdoor cameras are motion-triggered so depending on what they’re watching, they shouldn’t be recording constantly with hours of dead air.
Everything is USB-compatible for easy backup, but you’ll have to purchase an internal hard drive separately. But at this price, the overall cost of the system shouldn’t be prohibitive.