In older electro-mechanical controllers, the cycle is sometimes referred to as a?

Answer: B — Dial

In older electro-mechanical controllers, the term "cycle" often refers to a dial. This is because these types of controllers utilized a mechanical system where various cycles of operation were indicated by a dial that rotated to display the current phase of the signal cycle. The dial would visually represent the timing intervals of the signal phases, giving users a clear view of the progression through different states, such as red, green, or yellow lights. The use of a dial provides intuitive feedback on the timing settings, allowing technicians to easily set or adjust the cycle lengths for each signal phase. This mechanical representation is a hallmark of electro-mechanical controls, distinguishing them from modern electronic controllers which may provide digital displays or other more complex representations of timing functions.