Analog linear encoders

Hello.
I have an old milling machine (1989) that has linear scales installed.
Scales seems to be analog sin-cos 1Vpp they have 6 wires go to old controller.
How to identify the wires and how to connect to mesa fpga card ?
Can i do a circuit to convert the sin-cos wave forms to square A-B that accepts mesa card?

Is better to replace these scales with digital scales that output square AB differential signals ?
With 280euros i get 3 new digital optical glass scales + 3 axis DRO

So what to do keep the old scales or to replace ?

Can i use this ?
wiki.linuxcnc.org/cgi-bin/wiki.pl?ResolverToQuadratureConverter
Can arduino one code upgraded for arduino due (has 14bit analog inputs) ?

Thank you.

Witch Heidenhain EXE to get ?

Heidenhain Encoder Interface EXE 702 B is ok ?

I see that exe is for 11 μA PP and IBV for 1Vpp

EXE or IBV box to get ?
anyway i will try arduino for first time..
How to make the 1mbs uart connection with mesa ?
The arduino code is for quadrature..

Exists somewhere mesa smart serial protocol description ?

I just picked up a surplus XY table with linear encoders. Unfortunately the encoder label was on the back side and of course are not ttl.
Mine output uApp. I'm looking into converters from the manufacturer but was hoping someone here has a solution for the sine output in micro amps. I wish Mesa had a converter for these things???