Awww, take pity on the poor guy: everybody has to start somewhere, and most people can't tell you how a dBm and a dBv differ, or why. If you haven't had to build a patchbay yet (or optimally drive a 600 ohm load), why the heck would you know? It wasn't tattooed on the back of my neck at birth- I hadda ask someone too, back when the Earth was still cooling.
Anyway, the benefits of a patchbay: Packaging, and longer life of most of the important cables in the studio. Using a patchbay allows the basic interconnect to be set-and-forget, and allows the cables that take all the flexing and daily abuse to be short, easily tested, and easily swapped. The reliability benefit _cannot_ be overstated: If by some mischance you need one special 13.7 foot cable that terminates in a 3.8mm stereo plug to connect your prized vintage Frobifier 200 to your board, chances are that you won't want to inventory a spare. And if the cable fails mid-session after it is unplugged for the umpteenth time, you're _screwed_. Better to make that cable be a permanent fixture, hide it behind the racks so that it doesn't get twisted, stepped on, or the piano rolled over it, and let the patch bay cables take all the abuse.
It gets even worse if you realize that the replacement 3.8mm stereo _jack_ in that prized Frobifier 200 hasn't been made since 1976, and if the jack goes bad from all that plugging instead of the cable... You get the picture.
In any case, normalling works as follows. Studio patch points are usually implemented with pairs of jacks: the upper jack, by normal convention, is a signal source (an output). The lower jack is a signal destination (an input).
Open, or non-normalled: the upper and lower jacks are completely independent. They don't talk to one another at all by default, so to establish signal flow, you have to plug a patch cable from one to the other.
Full normal: There is a default ("normal") connection made between the upper and lower jacks of a pair. They default to being connected whenever there is nothing plugged into *either one of them*. Sticking a plug in the upper disconnects the default signal route from the lower ("breaking the normal"), so you have to run another patch cord into the lower from somewhere if you want that destination to be driven. Ditto with sticking a plug in the lower. Important point: a plug inserted in either jack of the pair will break the normal.
Half normal: this is IMHO the most useful type. There is a default connection from upper to lower, just like the full normal. However, it is set up so that plugging into the upper (source) jack _does not break it_. This provides you the ability to parallel two loads on a single source (i.e., a freebie two-way mult, since both your patch and the default destination are driven). Important point 2: *Only* plugging into the lower jack breaks the normal.
Parallel: the jacks are connected without any normal switching (they are hard-shorted in parallel, whether anything is stuck in them or not). This is also called multing. I usually put 3 or 4 4-way mults in any patchbay I build. Mults typically run horizontally, since in the old Switchcraft telephone style patch bays the solder lugs all line up, so you can just stick pieces of tinned wire straight along and glom 'em together.
The more "modern" prepackaged TRS patchbays (simple 1/4" TRS jacks on the front and back) made with PC board mount jacks can be a little harder to do mults with. No problem for me, since I don't use 'em. I'm a throwback: I like the old telephone-style longframes, because I've never yet had one fail unless it was _mercilessly_ abused. And the Switchcraft telephone style patch cords cost $20 a pop because they are the next best thing to immortal...
Just about the only thing that will kill a longframe jack is sticking a regular (stereo-headphone-type) 1/4" TRS plug in it too many times. The real telephone-style TRS plugs have that funny empty-condom tip shape to keep from overstressing the spring contacts that do the normalling for you. I always build a single space rack strip with 5 or 10 non-telephone 1/4" TRS jacks, and a few XLRS of either sex, wired to open jacks in the the Switchcraft bays as access points for funny cables. Seems like you're always needing those, and it makes the real patch bay much longer lived to not have those ugly TRS plugs shoved into 'em...
Hope that helps!
