The card we are looking at here (labeled RP64) is an RP4-H card. RP4 stands for Regional Processor Generation 4 being a newer version of the traditional AXE10 BYB202 Regional Processor.
The primary benefit for RP4 is that it is co-located in a subrack with the Extension Modules (EM's) that it controls. In AXE10 RP's control EM's and EM's control devices.
The RP4 is only found in BYB501 / AXE810 generation of AXE10 and does away with parallel buses, instead having a serial bus cable as seen above RPB S/O and RPB S/I. (Serial out and Serial in)
These buses are actually cables that are cabled directly back to the Central Processor (APZ212*33 in the above case)
The above picture shows the hardware architecture of the generic device magazine, also known as a subrack. As I said above, in AXE10, RP's control EM's and EM's control devices which can be clearly seen in the picture.
CP controls RP4 which controls the EM's which contain (and control) devices. A device can be any entity that provides a service such as a line circuit (LIC) on a line board (LIB) for instance. An example of a LIB in AXE10 is ROF 137 4442/1 LIC12.