DC-10615 comes from a different series of documents within the same North American manufacturer, and the distinction between the series is worth understanding because it reflects how the company organised its requirements. One series carries the requirements placed on electrical and electronic components, stating what a unit must achieve and under what conditions, while others carry test methods, design practices or vehicle level requirements; a supplier receives the numbers that apply to the work and is expected to assemble them into a coherent programme rather than to treat any one of them as the complete specification. A document of this kind therefore has to be read alongside the test method documents of the same manufacturer, since it states the level but not the procedure by which the level is applied. That separation is a common source of confusion in a first project with a new customer.