5-pin network cable? (similar to cat5e)

Hello, Recently I've got my hands on a Televideo TS-803.
Sadly, the cable to the keyboard is broken and the only way to fix this is to get a new cable.

Now, the wierd thing is that the keyboard uses a 5-pin network cable.
I can't find any information about this on the internet, because the official standard cables are 2,4,6,8-pins.

Any suggestions would be appreciated.

(Might have posted this in a wrong place.)