TiVo stepped up its efforts to defend a core part of the technology behind its digital video recorder on Wednesday as it sued AT&T and Verizon over their own fledgling television services.

The complaints, filed in federal court in the eastern district of Texas, echo similar cases TiVo brought previously against Dish Network and EchoStar, the two largest satellite television companies in the US. TiVo won those cases, though both are now under appeal. Also, the US Patent and Trademark Office has begun a re-examination of the key patent behind TiVo’s time-shifting service, which allows users to digitally record television programmes.