If you are replacing a specific unit for a bulk account or specialized setup, these are the most common models seen in the secondary market:
Comcast Digital Adapter DTA Self Installation Kit DCI1011COM Go to product viewer dialog for this item. buy digital adapter for comcast
A very small, basic unit designed to bring digital channels to older analog TVs. Xfinity Dc60xu Hd Digital Transport Adapter | HDMI eBay - thetophatcat Go to product viewer dialog for this item. If you are replacing a specific unit for
Often sold in complete kits including a remote and power supply. It is firmware upgradeable and uses composite RCA connections. Composite Video RCA
Comcast Digital Transport Adapter DCI1011COM, Self-Installation Kit, Firmware Upgradeable, Composite Video RCA, Black | AVI | Single Core