As already stated by the chaps above SRE is the kit that gives you a SRA.
Think a less accurate ILS that talks to you rather than deflects needles; or a PAR with azimuth only.
Typically the controller will give you headings to maintain the centreline and height information to maintain the correct glide path E.G. G-XXXX turn left heading 272, passing 4 miles your altitude should be 650 Feet.
This continues until your minima where you will maintain a Minimum Descent Ht/Alt until you either get the references required to land or reach your MAP; where if you dont have references SOP is to poo your pants, look at the fuel guage and try again somewhere very close.
