The field, tenor and mode of the context of situation function “as a point of entry to a situation as a set of possibilities” (Halliday & Hasan, 1985, p.55). Within a culture, there are sets of certain recurring situations with the same values of field, tenor and mode being present, or “a specific set of values that realises field, tenor and mode” (p.56). This can be termed the Contextual Configuration, or CC. The example Hasan gives is of a service encounter – buying oranges – which has a clear recurring set of field, tenor and mode values.
Contextual Configuration is “not the statement of one specific situation, but rather…the expression of a type of situation” (p.102, their emphasis). So, the CC is not like a snapshot view of one situation, or the “material situational setting” (p.99) of the physical environment where the text takes place (although an individual text may be affected by it), but is instead instantiated through many instances of the same type, “a particular calibration of values frozen at a particular point in delicacy for a particular purpose” (p.105-6).
I think a good example is the US Supreme Court. In its history the Court has occupied a number of different buildings (and not just in Washington) and there have been a number of Justices, which is the material setting, yet the Contextual Configuration of ‘Supreme Court’ has essentially remained the same since its inception. It is made up of certain recurring sets of practices codified as texts that remain constant and are re-produced over time.