Remote kit, voltage?

Years ago i Ebayed this popular cheap 4ch 433MHz remote control kit. Now that i found a use for it (arduino/ Led-lightning), i have no clue what the RX voltage should be.

I found the TX use 12V battery, that’s ok, but for the RX no data can be found. Now running 5V to be safe. However, range is only a few meters, even with a 17cm wire-antenna.

Maybe you remember this kit, and/or have the same and can help with voltage and possibly the range problem? Thanks.

like this one ?remote control kit

It's 5V receiver.
Did you check your remote fob battery is good?

Also, I wouldn't be surprised if it's 315mhz.