https://www.heidenhain.in/products/encoders/angle-encoders/modules/srp
Absolute and incremental SRP angle encoder modules HEIDENHAIN
The SRP angle encoder modules use inferential scanning, with a phase grating as their measuring standard.
angle encoder modulesabsoluteincrementalsrpheidenhain
https://www.heidenhain.pt/products/encoders/angle-encoders/modules/mrs
MRS angle encoder modules for rotary and tilting axes HEIDENHAIN
The MRS 2000 angle encoder module delivers high repeatability and convenient installation to rotary and tilting axes.
angle encoder modulesmrsrotarytiltingaxes