[citation][nom]Emperus[/nom]Correct me if i am wrong but rectifiers as i understand them are basically used for ac to dc conversion.. I can understand using diode(s) on a reverse current (dc line) protection role as diodes block dc.. But this very nature would make them unsuitable to be used in forward dc current paths.. And batteries do produce dc current..[/citation]
I once stuffed and soldered circuit cards for a company in the medical industry. One of their products was powered by a 9V battery, but had no polarity indication. Instead, it indeed used a simple 4 diode bridge rectifier so that the device would get the correct polarity of DC voltage no matter which way the 9V battery was installed.
So indeed, this is nothing new. However, the article says there are two contacts per battery. So I am guessing that this is not a bridge rectifier. Especially since you would need a bridge for each battery, and each bridge would drop .8-1.2V of the batteries 1.5V (two active diodes dropping .4-.6V each), leaving only .6-1.4V of battery power available, assuming brand new batteries. Instead, this looks like there is some sort of polarity sensing logic involved, since there are two sets of contacts per battery. A bridge network would only require one set of contacts per battery.