These are the original TiVo units offered by Philips, Sony and Hughes. The easiest way to tell whether or not you have a Series1 is to look on the back; these units do not have a USB port (or an Ethernet connector). Standalone units are the ones that work with your cable, or an external box for cable or satellite. DirecTiVo units have built-in DirecTV and require a subscription with DirecTV. Discussion of upgrades, software mods, TurboNet, and CacheCard adapters is welcome here.