To paraphrase my old college econ professor, it's obvious to even the most casual observer that digital terminal adapters have been a big boon to Comcast's bandwidth needs.

Comcast was an early proponent of reclaiming bandwidth via DTAs, and through the second quarter, it had more than 20 million of the devices – largely self-installed by customers – in subscribers' homes. Augmented by its aggressive use of DTAs, Comcast has its all-digital conversion project completed in 90 percent of its footprint and expects to have it finished by year's end. Comcast's all-digital conversion, which Comcast internally calls Project Cavalry, has freed up bandwidth for more HD channels and DOCSIS 3.0-based data tiers, among other services and applications.

Next up for Comcast and other cable operators: HD DTAs, some of which started cropping up at The Cable Show earlier this year.

"That [HD DTA] is a spec that is being developed out of Comcast much in the same way that we developed the original SD DTA specs," said Steve Reynolds, senior vice president of home networking for Comcast. "We're going to be field trialing those devices later this year, and, in fact, some customers may even get HD DTAs before the year is out."

Reynolds said the original SD DTAs were derived from a chip that was built for the off-air transition.

"They didn't have the HD output capabilities," he said. "They were intended to be a device that sourced analog televisions. The silicon development cycle takes time. It took us time to build the device, but there's no question about it that we want to give HD-quality video to the subscribers that have TV sets that can use that signal."

While some cable operators have opted for DTAs, others have used switched digital video (SDV) to boost their bandwidth, but at some point they may choose to do both. Catherine Mitchell, Cox Communications' executive director of video product management, said that while Cox doesn't currently have any DTAs in the field, "we are considering those as an option in the HD environment going forward."

At this year's Cable Show, Nagra announced that Cable One had selected its HD DTA, which is made by Korean vendor Digital Multimedia Technology (DMT), while Motorola was also showing an HD DTA.

Ken Morse, chief technical officer of Cisco's Service Provider Video Technology Group, said Cisco would be trialing its HD DTAs shortly. Motorola's Evan Groat, senior director of product management for set-top boxes, said his company's HD DTAs would be coming out later this year and into the first quarter of next year.