You do not need to split the cable input to get dual tuner functions, its already there. To view what is on the other tuner, just press LIVE TV button and it will switch between the 2 tuners each time its pressed.
Sooner or later, when your cable company switches to digital entirely, you would need 1 Multi- or 2 single stream cable cards to view digital channels.
You can also add a UHF/VHF antenna to receive Over The Air digital signals, and that is what goes to the ANTENNA INPUT.
I only use OTA no cable and get 40 digital channels, where before the transition, I only got 10 analog channels.
Series 2 (PLS, sold)
TiVo HD 1TB (157 HD Hrs, PLS, "652")
Roamio! Oh, wait, Its Juliet!
OTA! OTA! OTA!
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!