If the red hall call inputs are high, you have Bi Logic controls. You put a call in by grounding the input. If the inputs are low you put calls in with 120vac to the input. In later years they had a 24vdc input system. But I believe yours is either 120vac, or Bi-logic. As for the dispatch question, the Miprom 21 used the first two cars in the group as serial communication dispatchers. In the older analog drive era, they used the common panel, and parallel communication to answer hall calls.