The Lionel 90C controller is a 2-terminal momentary push-button single-pole switch that closes a single circuit.
Each button in the UCS controller closes two circuits - as can be decoded by studying what I call the "stacked-leaf" design in this widely available diagram:
Hence the previous link to a dual-pole switch to exactly emulate the connections made by the original 2-button controller.
But all is not lost. Take a look at this OGR thread. You have to slog thru the fine-print but for the vast majority of applications you should be able to perform the uncoupling function with a single-pole switch and, separately, perform the unloading function with a single-pole switch.
