The sat-nms ACU19V provides the possibility to connect two different types of angle encoders: optical SSI encoders (S) and Resolvers (R). Please refer to chapter Interfaces to the antenna/ Pin descriptions for more detailed informations. You have to decide at point of order which variant you want to have. The angle encoder type is specified by an add-on to the name of the unit. The sequence is azimuth, elevation, polarisation An example: ACU19-SSR contains SSI interfaces at azimuth and elevation axis and a resolver interface at polarisation axis.