137.The “mushroom growing apparatus” seems to be a combination of various separate machines. However, on applying the relevant section notes and Explanatory Notes, it appears to us that mushroom growing apparatus does not qualify as: (i) a composite machine, as the different machines are not meant to be fitted together permanently, or (ii) a functional unit, because all the machines do not appear to work together towards a single, clearly defined function. Rather, each machine, i.e., the head filling machine, the automatic watering system, and the compost spreading equipment, seems to perform its own independent task. The only common element is that they are all part of the broader mushroom cultivation process, which is different from fulfilling a specific, unified function. To illustrate, according to the Explanatory Notes, an irrigation system comprising a control station with filters, injectors, metering valves, underground distribution, branch lines, and a surface network would be considered a functional unit. Conversely, closed-circuit video surveillance systems, which include a varying number of television cameras and video monitors connected by coaxial cables to a controller, switchers, audio receiver, and possibly automatic data processing machines (for data storage) and/or video recorders (for recording pictures), would not be regarded as a functional unit.