  In large process control systems it frequently becomes desirable to establish
feedback relationships that were not anticipated during the design phase of the
project. The "Generic Lock" architecture discussed in this paper makes it
possible for system operators to implement new feedback loops between arbitrary
process variables quickly and with no disturbance to the underlying control
system. Any available process variables may be selected for the input and
output of the loops so created, regardless of their physical or logical
separation. The system allows multiple user interface points distributed
through the control system while ensuring consistency among the feedback loops.
This system can be used to quickly prototype and test new control philosophies
or to control temporary hardware arrangements without any new software
development. It is implemented at the Thomas Jefferson National Accelerator
Facility using the Common Device (CDEV) framework on top of the Experimental
Physics and Industrial Control System (EPICS). This paper discusses the
architecture, implementation, and early usage of the system.
