That box is the on/off switch for the Tascam. I just swapped out the non-polarized plug that attaches to it, for a polarized cord.
You'll find the power cord attaches to it in 2 spots, as well as 2 wires going to the transtormer.
The set up is:
A - Wire from power cord and wire from transfomer together. This is the Neutral.
B - Wire from power cord. This is the HOT.
C - Wire from transformer. This connects to HOT when the power switch is in the ON position.
If you want to change out your cord to a polarized cord, you would take out the old one, and wire it so the wire with the wide blade connects A. The wide blade on the plug is Neutral, and on the left when plugging it into the outlet. The smaller blade is the HOT, and is the one you always want to have switched. That one would connect to where the old wire is by itself on the switch. C, the wire from the transformer, remains where it is.
If you want to instead, add a 3 prong cord, you'd do the same, but the 3rd wire (green on the cord) would be soldered somewhere to the chassis (metal frame/body) of the Tascam.
Generally the color code would be:
White - Neutral
Black - Hot
Green - Ground
On the Tascam 244 (at least mine), the two colors are brown and white. In the manual, page 52 says the colors are blue (neutral) and brown (live, aka HOT). Blue connects to the terminal marked N or is colored black. Brown is connected to L or the one colored red.
I think for Blue and Brown, they are refering to the color on the power cord, as there is no blue wire inside the unit. Instead, I think they were brown and white.