Hello aspirant,

You can join Department of telecommunication (DOT) in India by filling out the form which are made available by the department when vacancies arises. You have to keep checking there website and look for vacancy and than fill the form, there are different posts and different requirements for each posts so that have to be taken care of but as you mention about an engineer of Electronics and communication, if you are a fresher with no experience than you can join in as junior engineer and move up the grade, and if you are with experience than you can switch according to the vacancy or apply regarding the same,

I hope this clears somewhat your doubt.