Key point, the switches are normally open. In order to say select transformer conventional operation, the GND and Transformer remote pin get shorted together. So GND is common for the control switches, and then the 3 switches are normally open for smoke, sound, and remote/bluetooth to be functional. That makes testing easy as you don't need to plug in a switch harness, just apply power to the board with the socket open circuit and that represents normal operation in LC+ bluetooth or remote mode.
This board is from this engine http://www.lionel.com/products...us-rs-3-101-6-84698/
Connectors for switches, electrocouplers, LED lighting, speaker, and smoke unit are all JST-ZH 1.5mm pin spacing. 2 pin for electrocouplers, 3 pin for speaker, 4 pin for switches, 4 pin for smoke, and 5 pin for LED lighting.
Connector for the motor is JST-PH 2 pin 2mm pin spacing.
Power in is the same standard Lionel has been using, JST-EH 2 pin (or equivalent).
Connector for the motor is JST-PH 2 pin 2mm pin spacing.
Power in is the same standard Lionel has been using, JST-EH 2 pin (or equivalent).