Zenith's DTT900 is an ATSC tuner, a set-top box that receives high definition television broadcasts and outputs their signals for use by older SDTVs. The DTT900 is part of a larger group of ATSC tuners included in the government's DTV coupon program, helping users upgrade their older sets before the analog TV shut-off in 2009. The availability of these coupons effectively takes $40 off the cost of any of the included models.

The DTT900 outputs downconverted standard definition video over either a set of composite A/V plugs or RF modulated over a coaxial cable. An on-screen EPG shows upcoming programs from a list retrieved over-the-air. Zoom options let the user watch widescreen programs letterboxed, or zoomed-in, cropping off the picture's left and right sides. Reviews cite the DTT900's excellent reception capabilities, but note sub-par audio performance, with low-bitrate-MP3-like artifacts noticeable.