Let's consider what is these days a heresy: Corporate Communication is separate to Public Relations. The two operate largely in isolation, similar to the Marketing and PR silos described in the A ("Apart"/"Silo") model.
We will call this Model X, and illustrate it using the following model:
In Model X, PR and Corporate Communication are separate. PR handles all communications targeted at external stakeholders; Corp Comm creates all communications intended for internal stake holders.
Simple? Perhaps. But in companies that offer technical goods and services, can such a separation be operationally realistic? Must there not be some informational overlap? If the public require product knowledge, yes. If internal communications contain product information, yes. Given the certainty of these practical requirements therefore, how can these two functions be isolated? Stakeholders - both internal and external - will have technical information requirements, but the model features no such explicit linkage illustrating the mode or source of this adhesive.
Might this be our answer?
In the "PTC" model, we see Technical Communication occupying the centre ground. In companies that operate this model, the technical information required for both internal and external stakeholders is created in the Tech Comm department. Depending on its direction of travel, i.e. to the public (exterior) or to in-house users (interior), the raw technical information is crafted in the appropriate area of overlap. If, for instance, technical information is needed for advertising copy, original authorship of that information (not any surrounding copy) occurs in the Tech Comm sphere, but a translation of that material occurs in the oval of intersection between the Tech Comm and PR sphere. This is because the PR author, not the technical communicator, is best suited to the task of reworking the material so that it is audience-appropriate, i.e. fit-for-advertising-purpose or Tweet-friendly.
Likewise, if technical information is required by top-level management, a translation occurs in the lower oval that forms the intersection of the Tech Comm and Corp Comm spheres. For strategic purposes, management will need to know some details of a product, but likely not all. Hence, the workers in this sphere of intersection perform a different, but still important, translation-through-rewriting, to ensure that only what is needed is conveyed, and all that is conveyed is presented in a digestible, readily comprehensible format.
Perhaps we should label the intersections "zones of translation".
Naturally, if multiple languages are involved, the surface area/intensity of work and the criticality of these zones expands. Individuals capable of translating technical information in one language into native-appropriate advertising copy in another language for a particular demographic overseas are likely extremely high value persons.
Thus, in the PTC model, the Tech Comm worker or department functions like an information supplier, whose work rarely reaches its audience without significant crafting by PR or marketing experts (if the information is destined for consumers) or a Corp Comm writer (if the material is needed internally, e.g. for meetings and reports).