To lower the voltage of the battery pack to the required voltage, [Alan] grabbed a 1N4148 diode and put it in series with the battery pack, which also helps prevent any accidental reverse polarity.

[rawe]’s simplification of this is to get rid of the transistors and just plop a single 1N4148 diode in there. This would of course be useless without the software to communicate with 1-Wire ...