A Digital transport/terminal adapter (or DTA) is a device used by cable companies who are switching to all-digital cable systems. They typically have an RF input for receiving service, and a modulated output on Channel 3 or 4 that allows a TV to be set to channel 3 or 4 and have the tuner change channels. They are also deployed by cable companies who are encrypting digital signals to cut down on cable theft.
These devices go under several names, such as Digital Terminal Adapter, Digital Transport Adapter, or Digital Adapter. They generally do not offer pay-per-view or DVR support, but Rovi (formerly Macrovision) is deploying an on-screen guide that would allow subscribers to see what is on TV at the moment. Digital adapters are intended for rooms with less used TVs or for basic cable subscribers.