Your Oldest Machine Is the Easy One: Connecting Legacy Equipment Without Replacing It

Brownfield connectivity projects begin with a machine list sorted by age, and that is why they stall. The machines that never get connected are rarely the dark ones — they are the ones nobody is allowed to touch. This guide reframes legacy as a permission state rather than an age, sorts a mixed machine park into four bands by what each control actually emits (a standard information model such as umati over OPC UA, register access over Modbus TCP, MTConnect, bare contacts, or nothing at all), and names the three failure modes that follow from getting the framing wrong: the retrofit reflex, the parallel plant and the snowflake fleet. Includes the warranty, NIS2 segmentation and works-council decisions that set the real schedule, a five-question vendor evaluation framework, and a twelve-step implementation checklist.