What app can I download to work a kirsch k3 5.1 check surround receiver

Generally none, but there are some far-out answers here.

https://www.techhive.com/article/599621/how-to-use-your-mobile-device-to-control-your-home-theater.html

https://www.google.com/search?q=kirsch+k3+system+app

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If you wish to get more details; check the sites linked here. It has set-up code list & set-up procedure to many popular brand remote controls.Common codes to check devices with different brand TVs are given, in the order of the device's brand name list in alphabetical order.Pull up older posts. Surf the site with patience.
http://remotesearch.blogspot.com/
http://electrohelponline.blogspot.com/

Using the search feature on the Xfinity remote with my Kirsch system I could find no codes for it. Am going to purchase a better multi remote and will let you know how that goes.

Yes lost it wen moving

prob need to goto manufacturer web pasite and order one.

u wont be able too without a receiver of some type (surround sound or amp)

Um, the remote is battery powered, right? So it would be unaffected by the loss of house power. I'd say your central unit has taken a hit, not the remote, but you could try new new batteries. It may just be coincidental that the remote died when it did.

'ai besoin une remote pour un receiver fm et am kirsch loud speackes k3 pouvez vous m'aider svp

If your unit is not listed within the list of acsess codes, you will have to find it the old fashioned way. Code search is available on all multi function remotes. It takes awhile but it will eventually work. You might also try going to the manufacturers site and check in the "support" option or the FAQ's Thanks, Dana

If there are no codes in the manual then you may have two options left for you. You may order a 20 or 21 remote from Dish after verifying it will work with your system with customer service or you may get an ALL IN ONE REMOTE. Thanks for using Fix Ya and let me know if you need further assistance.