Here is my Whistle/Bell controller. The white wire is coming in from the D post of the transformer, the black wire goes out to an old fashioned cab control matrix of 8 barrier strips & toggle switches, that flip control of a particular block from the left handle to the right handle. The smaller wires go to the terminals of a DPDT toggle to activate either the whistle or the bell.
Oh, and I should mention that yes, the horn or whistle & bell work fine.
