Connectors for use in large scale trains 2 pin connectors Note: JST connectors are pretty common, and are often used in the hobby. They lock together, carry reasonable current, and are relatively compact. All Electronics, www.allelectronics.com, they carry a lot of different connectors already wired. This is where you can find the JST connectors used by Aristo and USAT. https://en.wikipedia.org/wiki/JST_connector 2 pin JST SM connector, used by Aristo and USAT - All Electronics part number CON-240 This is a good general purpose connector. USAT uses them for motor blocks and Aristo uses them for the "MU" connector between locomotives. It really cannot handle really high current, and if you leave them open and to the weather the contacts can develop resistance. These are used on some of the older locos on the motor blocks, like the Aristo FAs: CON-230P also known as JST RCY connectors Here is the matching socket: CON-230S Small 2 pin connector: SBC-1 Pins are spaced 2mm apart Small 2 pin connector SBC-2 Pins spaced 2.5 mm apart. 3 pin connectors 3 pin JST SM style CON-340 Nice for internal inerconnects between decoders and the shell or chassis. 4 pin connectors 4 pin JST SM style connector CON-440 4 pin version as above for the rest of the JST SM connectors. 4 Pin "molex style" CON-104 Higher current, best for motors and track pickups and batteries. You cut the wire in the middle and you have a 4 pin connector pair. Aristo 4 pin connector used on Prime mover blocks, 2.5mm pin spacing, Molex SPOX, series 5264, part number 0050-37-5**3 where the asterisks are the number of circuits. In this case the exact part number is 0050-37-5043. I found the pins are sold several ways and in several finishes, bulk from Digikey 0008-70-1040 (bulk) and 0008-70-1039 (each), thse handle 22-28 gauge wire The crimper is expensive The header for the pcb is series 5267 and 5268, the terminal series is 5263 6 pin connectors 6 Pin JST SM style connector CON-640 6 pin version of JST SM, good for connecting decoders to components in shells, chassis or between steam loco and tender 8 pin connectors I found 8 pin JST SM on ebay: 10 pin connectors CON-2410, Connector used by Jim Carter in some LGB conversions All Electronics also has the matching headers, the site will typically show you the part numbers when you look up a connector.