Mandatory testing and certification by TEC
TEC, India's Telecommunication Engineering Centre, will be responsible for the approval of any telecommunication equipment - they have released the final document Mandatory Testing and Certification of Telecom Equipments (MTCTE). Beginning October 2018, such certification will have to be done prior to importation and will be nominally limited to 5 years. Devices for the phone network will follow the Simplified Certification Scheme (SCS), whereas packet switching devices will be subject to the General Certification Scheme (GCS).
On their website, TEC also offer further help like FAQ and technical requirements: