> My reading of the Qbus spec is that P OK and DC OK are active high. That > diagram
They are, for a very logical reason. Remember you can wire-AND open-collector signals -- that is link them together so that any driver can pull the line low and the line will only be high if all driver transistors are cut off. Now if you have a large system with multiple boxes and power supplies then any supply can pull P OK and DC OK low if there is a problem. Only if all supplies are present and correct will the signals be high. -tony
