The question is one I have often wondered about myself and although I know you have devices to inject DC on an AC supply and they are used with stone crushing plants I have never really studied them to find out what exactly they are for.
Of course we have the same in our home where we want to power an amplifier on an aerial mast and it sends AC down the coax at the same time as DC is sent up to power the device.
We have two components the inductance and the capacitance the first will allow DC to pass and not AC and the second is the reverse.
However the question was rather open and really a little more is needed before one goes deep into the answers.
Could of course be completely wrong and may be he was asking about
Kev, asking basic questions then insulting forum members is one thing, but this is not the place for making offensive comments about the greatest Rock 'n' Roll band the world has ever seen.
Buy yourself a basic electrical theory book and a copy of "For those of you about to rock (we salute you)".
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local