Does MagicJack Work On A Cordless Phone?

yes you can use a cordless phone with MJ

your initial question of can you use a cordless phone with MJ seems to differ from what you are asking...

does the phone in the other room have dial tone from a land line provider, or other telephone service connected to that jack? if not, then you can just connect a line cord from the MJ to the nearest jack, and all of the jacks in your home will be connected to your magic jack dial tone...

otherwise you just need to use a 2 way splitter at the magicjack to connect a corded and cordless phone to the MJ at the same time..

If you use MagicJack, you will no longer require phone service from your local telecom provider. Once MagicJack is set-up, you will be able to answer incoming calls on your MagicJack number and make free outgoing calls. MagicJack requires a broadband Internet connection and a computer to operate. You should not rely on MagicJack for emergency services or calls during power failures. If your Internet service is provided through Cable, Fiber Optics or a Wireless connection, you can immediately cancel your existing phone service. If your Internet service is provided through DSL, you will need to contact the telecom and explain that you want to keep your Internet service but disconnect the phone service (also known as "dry loop" or "naked DSL"). They may charge you a small monthly fee for this privilege and with some DSL providers it's not possible to disconnect your phone line and keep Internet service.

Connect a phone cord from the magik-jack to the wall jack, this should make all jacks have dial-tone, or connect a cord from the magik-jack to a line splitter - connect the line splitter to the wall jack and plug one of your phones into the other side of the splitter, and you should get dial tone on all of your other jacks.

Line Splitter pic:

http://www.pccable.com/images/02300.jpg