The 21-HWM (21-pin HardWire Male) is a circuit board with a 21-pin NEM660 (MTC21) connector and solder pads to connect wires. The male 21-pin socket may be used with any 21-pin decoder such as the WOW121 or EU621. The decoder can then be hardwired directly to your locomotive, or used with a plug-in harness. The 21-HWM is great for situations where space is limited and a full-size motherboard cannot be used. A pin-out of the 21 pins can be found Here.
To solder wires to the provided pads simply:
Each pad on the 21-HW-Male is labeled. These pad labels are as follows (from left to right with pads facing you)
| Speaker (-) | Speaker(+) | Function 6 | Function 5 | Function 4 | Function 3 | Ground | CAM/Aux Input |
| Function 2 | Left Rail (Black) | Motor (-) (Grey) | Yellow (F0R) | White (F0F) | Blue (12V+) | Motor (+) (Orange) | Right Rail (Red) | Function 1 |
IMPORTANT NOTE (NEM660): The 21-HW-Male connector does not feature output transistors on Functions 3-6. These outputs will be logic-level from the decoder unless otherwise specified by the decoder manufacturer. If you need to use these function outputs from the decoder, a separate logic booster may need to be added externally.