The K-27 is the first Large Scale locomotive with totally isolated electronics, which allows for easy installation of the control or sound system of your choice. There are two sets of switches; the lighting switches behind the smoke box door at the front of the locomotive, and the control switches underneath the coal load in the tender on the main PC board.
    There are three switches behind the smoke box door at the front of the locomotive: Smoke, Cab Light, and ML & FF - which controls the classification lights and firebox flicker. Each switch has a DCC position, a DC position and a center off position.
    There are three switches on the main PC board in the tender.  To access these switches pull up on the front panel on the tender and remove the coal load.
    Pick Up Switch: In the "Track" position, track power is fed from the tracks through the track Polarity switch to the electronics inside the    locomotive.   In the "Battery" position, all track connections are removed and all power is fed through the two screw terminals just to the left of the Pick Up switch.
    Track Polarity Switch: This allows you to select Large Scale or NMRA polarity for your locomotive.
    Motor Switch: The switch controls the motor. In the "off" position, the locomotive will not move, but smoke and lighting will continue to operate.
    The K-27 comes equipped with an open and non-proprietary plug-and-play electronics socket. This socket is designed for after market plug-and-play products. There is a dummy PC board plugged into this socket which stays in place for normal DC operation.  The board is removed for use with a plug-and-play system. Each pin on the plug-and-play socket has a defined purpose and is labeled on the socket. Each pin is also connected to a solder pad for use with systems that do not support plug-and-play. 
    To install a speaker in the tender first remove the tender shell. Remove the two screws at the front of the tender underneath the coal load.  Remove the single screw under the rear hatch on the top of the tender shell. Carefully lift off the tender shell. A 3 inch speaker can now be mounted under the main PC board. To do this, remove the four screws on the four corners of the main PC board and carefully move it to one side. Solder the speaker leads
to the pins on the indicated in the schematic.  Do not let the speaker touch the PC board when you screw it back in place. Connect the sound system wires to the solder pads on the engineer's side of the main PC board if you do not have a Plug-and Play sound system.
    The K-27 is designed to support either two or four chuffs per revolution. The factory setting is for four chuffs. For two chuffs per revolution, remove the chuff jumper connection which is labeled JP1. 
    On board battery operations are possible with this locomotive. If your decoder is not plug-and-play, you connect the motor outputs of your decoder to the battery screw terminals. All function controls are then soldered to the function outputs on the Main PC Board.  Turn the Pick UP Switch to "Battery" and change the switches behind the smoke box door to DCC. There are solder connections on the circuit board for Tender Light, Chuff, Firebox Flicker, Class Lights, Smoke, and Cab Light.
    In all, this is a well thought out locomotive electrical system that will accommodate many control and sound systems. No major disassembly or "surgery" is required for DCC or Battery operation as is the case with many other locomotives. The instruction booklet that comes with the locomotive is extremely well written with photos and diagrams to help you with your electrical connections for this locomotive.