When a presenter on TV or Radio extends the greeting

Question: If the presenter on television or radio extends the greeting (of as-salaam `alaykum) or (likewise) the writer in a magazine, then is it obligatory upon us to respond (by saying wa `alaykum as-salaam) in this case?

Response: It is obligatory to respond (by saying wa `alaykum as-salaam) to the greeting (of as-salaam `alaykum) if a person hears it directly or by way of written text directed to him, or by way of a means of transmission directed to the listeners based upon the generality of the evidences regarding the obligation of extending the greeting (of as-salaam `alaykum); Allaah (Subhaanahu wa Ta'aala) says:
{When you are greeted with a greeting, greet in return with what is better than it, or (at least) return it equally}, [Soorah an-Nisaa, Aayah 86]
Shaykh Saalih ibn Fowzaanad-Durar an-Naadhirah fil-Fataaawa al-Mu`aasirah - Pages 642al-Fowzaan - ad-Da`wah 1502, Rabee` Awwal 1416AH

http://www.fatwa-online.com