If hardware, processors, network, transmission-channels or buses are central to your system, you should document or specify these hardware and infrastructure of your system in the technical context.
Especially for integrated hardware/software systems (embedded systems) you almost always need a technical context diagram.
The embedded systems context diagram above (especially on right side) is such an example.
However, it may also be important for information systems to show some aspects of hardware and infrastructure already in the context, e.g. for security issues (see the webshop example in tip 3-10).
For information- or web-systems, data-warehouse or business-intelligence, the deployment view (arc42-section 7) is usually sufficient and a technical context is rarely needed.