NEW DELHI: The Telecom Regulatory Authority of India recommended on Saturday that all DTH and cable set-top boxes (STBs) should support interoperability, and urged the information and broadcasting ministry to make it mandatory by introducing the requisite provisions.Interoperable set-top boxes will allow consumers to change their DTH operator without buying a new set-top box. At present, the STBs deployed by cable TV networks are non-interoperable — the same STB cannot be used interchangeably across different service providers. Trai also recommended the mandatory provisioning of USB portbased common interface for all digital television sets in India.