Designing switching systems for an automatic test system requires knowledge of the input/output signals to be switched and the test routine to perform the test. Automated test systems are usually designed with the flexibility to handle a variety of signals because test requirements change frequently.
The first step in designing a test system is to produce a Test Requirements Document (TRD), which outlines the system configuration and switching needs. Given that versatility is of utmost importance, designing the switching function may be one of the most difficult parts. To help design a switching system, one of the following switching topologies may be used, alone or in combinations. Figures Switch Topology, Scan Topology and Multiplex Topology describe the basic topologies.