Googling for "Speed Reference System" (SRS) doesn't immediately provide a wealth of information, but one of the links I found is an incident report and there is a paragraph that reads as follows:
"The FD pitch mode used for take off is SRS (Speed Reference System) which provides FD pitch commands to acquire and maintain a speed of V2+10 kt with both engines operating and V2 (or the existing speed if it is greater than V2) if one engine fails. The SRS mode normally remains engaged until the aircraft climbs to the thrust reduction altitude. Thereafter the FD pitch mode would usually change to CLB (Climb) or P CLB (Profile Climb)."
Hope this helps.