One gabba calls people up, is there a term for that?
Is there another gabba that instructs the gabba that does the calling up, as to who to call up? I've heard of a situation where one gabba may have it written down and tell the other who to call up, the name, like off cards. I've only heard of it once and not seen it. Is it common? Is there a source for it? Has anybody seen it?
I've also heard that one gabba calls up while the other does nothing. And i've heard that one calls up and the other is a "segun" he just checks that the reading is done properly, though i'd have thought they all check it. I found a source for a sgan http://en.wikipedia.org/wiki/Gabbai but does anybody know of a proper jewish source for the concept? like, shulchan aruch for example?