Have you ever wondered why some things in life are written in books and other, equally essential things, just never get printed? You have to learn them from trial, error, and ... more error. What I'm about to convey hasn't been written anywhere (to my knowledge). Yet it plays an essential role in the life of anyone who deals with technology, especially audio and video technology. It has to do with wiring strategy --- not the art of drawing schematic diagrams according to established electrical conventions --- but how to think when planning a complex system.
What follows is my opinion based on having designed and built
a half dozen TV studios and countless smaller projects. Other
opinions may be just as good, but if you have no opinion at all,
feel free to use mine as a place to start.
The need for wiring diagrams -
If you don't think this is important stuff, then maybe you need
to spend an afternoon tracing termination troubles in a wild web
of wires cloaking the catacombs behind stacks of equipment. Here
are some reasons for taking an active role in creating formal
wiring diagrams for any substantial system:
1. Sure, you can hook everything together, but a month from now
will you know what you did? Will you be able to trace the paths
from outputs to inputs when gremlins invade your equipment?
2. If technicians wired your system, will they remember a month
from now what they did? Will you be able to figure out what they
did if having problems in their absence?
3. Do your technicians use the system so often that they know
the wiring diagrams in their heads, and like to keep it that way
for "job security?" If so, they may be secure, but you
are not. How much do you want to rely on your technicians?
4. Which do you prefer, tracing lines on a paper or hacking your
way through a jungle of wire armed with a machete and a few expletives?
5. Is the system used by many clients and maintained by several
technicians? Until mental telepathy is mastered, paper is about
the only way to transfer wiring information from one person to
another.
6. Which do you think will be better: an off-the-cuff speech or
a speech that has been thought about, organized and re-organized.
Take it from an author, good articles aren't written, they are
rewritten. The same is true for wiring. Drawing the diagrams makes
you think. It forces you to solve some of your problems in the
paper stage where changes are cheap and easy to make.
7. If you built a house without any plans, how do you think it
would come out? Plans keep things orderly.
8. If you create the design and expect technicians to carry it
out, then of course, the design has to be written in a clear,
concise way. Not only do you avoid the errors of miscommunication,
but you aid your technicians in planning the construction. The
technicians see the whole picture at once and can buy parts and
set up space, and can organize the construction process efficiently.
It's comparable to going to an on-line edit suite with a well
defined edit decision list; the edit process becomes quick and
mechanical. You are not spending $400 an hour while professionals
and a room full of equipment stand around watching you think.
With a wiring diagram, you've done the thinking and except for
the inevitable surprises and changes, the installation should
progress smoothly.
9. The diagram gives others a chance to review your work and suggest
improvements before the plan is put into effect. The more expensive
and complex the system, the more you can benefit by the wisdom
(and yes, criticism) of others.
10. Patch bays, festooned with inputs and outputs, are notoriously
hard to read unless they are logically organized; specific inputs
and outputs are difficult to locate. Part of creating a wiring
diagram is to organize the content of the patch bays so that similar
things are grouped together. Even if patch bays are well organized,
when several are involved, it is still easier to glance at a wiring
diagram and trace a line to a certain place on a patch bay than
it is to read the patch bay, neck kinked at 45° , eyes squinting
to read the microprint, searching for a particular item. Anyway
you look at it, wiring diagrams and patch bays are synergistic;
the good logic that you put into one strengthens the other.
11. Many TV engineers have a tendency to build a system, then
add to it willy-nilly making the wiring and patch bays illogical.
Since they use the system every day, they get used to this randomness
and may not even notice it. For the rest of the world, the system
becomes hard to follow and tedious to use. In this regard, creating
wiring diagrams creates orderliness and counteracts the entropy
of random growth.
Here's an interesting observation: Have you ever noticed how computer
programmers dislike writing documentation for their programs?
And try getting building contractors to provide "as-builts"
showing changes in architectural drawings to reflect adjustments
made during the building phase. Police grumble a blue streak about
the reports they have to write and many teachers detest report
card time as much as their students. Similarly, most of the technicians
and engineers that I know despise documenting the web of magic
they weave behind the racks. Maybe it seems mundane, uncreative,
or too detailed to be any fun. Whatever the reason, documentation
seems to drain the adrenaline from technical people.
The role of the computer -
Assuming that you are convinced that you need a diagram, the next
question is whether to construct it on a computer or on old-fashion
paper. Personally, I use paper, but that's because I can't seem
to find the 10 hours or so needed to learn a computer assisted
design (CAD) program and don't have access to a plotter to print
out the results. If you have already climbed that learning curve
and have the plotter, then go for it, use the computer. I still
suspect that you'll find yourself sitting with pencil in hand
trying to draw the preliminary diagrams the old-fashioned way
before stepping up to the keyboard.
The thing I like about pencil and paper, at least in the preliminary
stages, is that there's no "technology" to get in the
way of your thinking. When drawing wiring diagrams, there are
a lot of details to juggle and the process takes intense concentration.
I find it necessary to draw as fast as I can once I get an idea,
sketching the interdependent facets before I forget them. Again,
if you don't find your computer to be a distraction, then put
it to work.
Getting organized-
It is not important that you are a fantastic draftsperson or that
you adhere to particular schematic "rules." It is important
that your drawings are clear and your symbols consistent. Have
a ball; develop your own conventions as you go along. Anything
that communicates clearly will do fine. Here are some of my thoughts.
The paper -
Have you ever tried to draw a map to your house and ended up with
3/4 of the streets squashed into the upper right-hand 1/16 of
the page? The same thing happens with wiring diagrams. I used
to draw them on large sheets of paper thinking I would have plenty
of room. Invariably the drawing would grow a thick matrix of tendrils
occupying 1/16 of the paper leaving the rest of the page blank.
Nowadays, I give in to my poor planning right from the start:
I use 8-1/2 x 11 or 11 x 17 pages, and when I reach the end of
a page, I attach another page onto it. The pages go wherever the
lines go without regard to form or beauty. When the whole works
is done, I tack on enough pages to fill in a rectangle of paper
and then reshape the drawing to better occupy the space. Remember
that step 1 should be thinking, not worrying about elegance.
The patch bays -
Most wiring diagrams involve patch bays. Since everything comes
together at the patch bays, they form the heart of the diagram,
the center of the web.
Because patch bays all look the same in structure but involve
a lot of lines and spaces, I hand-draw one blank patch bay, then
photocopy it to make the other patch bays.
Each patch bay gets a letter or number representing the input
side and the output side, and each connector gets a number. This
will be helpful in specifying the location of things later.
Actual patch bays have outputs on the tops and the inputs on the
bottom, thus signals flow downhill. On a diagram, signals flow
from left to right or downhill. This results in sources for signals
being on the left of the patch bay and the targets being on the
right.
Patch bays are either normalled or not normalled. Normalled means
that when there is no patch stuck into the socket, the signal
automatically travels from the output to the corresponding input
side of the bay. It is as if each output had a patch connected
to it feeding to the socket directly below it. On paper, it is
as if the signal traveled directly from left to right through
the patch bay. We indicate this normalling with an "N".
On the physical patch bay, I further affix a dot to indicate which
outputs are normalled. When a patch bay is not normalled, there
is no "N" and the signal doesn't travel anywhere unless
it is physically patched.
Where possible, leave room for growth. When going from one group
(say camera outputs) to another group (say TBC outputs), leave
a couple empty patch bay sockets. This way, if you add another
camera, for instance, you can list it on the patch bay next to
the other cameras (very logical) without moving all the remaining
connections down a slot (vary tedious).
Sources, monitors, and other gadgets -
It seems logical to put all the sources (ie. CD players, videocassette
players, etc.) in the same area of the diagram. That way when
you look for something on the diagram, you don't have to hunt
all over the diagram; you pretty much know where to start. Once
you've lined up your sources, you are likely to discover that
some items receive signals as well as send them (ie. audio and
video recorders). Now you have to decide whether to treat recorders
as something different from sources. This is a personal decision,
but I tend to put them with sources because most recorders are
also used a players and are therefore sources.
The signals fed to the sources have to come from somewhere, preferably
from the left of the sources. Invariably you are forced to send
signals wrong-way to the left on the page to feed the sources
that are on the left.
Once I have the sources figured out, I try to name and number
them in a logical sequence. The second audiocassette player might
be called CASS-2 or Pioneer CASS to distinguish it from its Sony
brother. Each stereo output would be represented by a pair of
lines, one marked L and the other marked R.
I like to group TV monitors together, especially if they are in
a console. I try to name them the same as their sources (i.e.
VCR 1, SAT 2, PRO, PREV, etc.). Sometimes this rule creates a
wiring nightmare because some sources are directly monitored (placing
the monitors near the sources on the page) and some switchers
have their own monitor outputs. They end up in different places
in the diagram forcing you to wrap the lines all the way around
Robin Hood's barn to keep the monitors together. So, I swallow
my compulsive adherence to convention and make two or more blocks
of monitors.
Switchers and audio mixers compete with patch bays as being the
heart of the system. It is hard to decide whether to draw a big
mixer and dangle patch bays from it or draw a big patch bay and
dangle the mixer and other stuff from it. If the mixer has more
inputs and outputs than will fit on one patch bay, then I let
the mixer be the center of the system and spread the patch bays
around. I generally put a feeding patch bay in front of the mixer
(to the left of it) and run the mixer's output to another patch
bay to the right of the mixer.
Parallel construction -
Once I have determined the sources, the monitors, the patch bays,
and the switcher or mixer inputs and outputs, I list them in a
parallel sequence. Thus, if on the left side of my diagram I have
VCR 1, VCR 2, VCR 3 in a row, the VCR monitors will run similarly;
VCR mon 1, VCR mon 2, and VCR mon 3 etc. The patch bay will keep
the same order: VCR 1, VCR 2, VCR 3. If these are inputs to the
switcher, they will go VCR 1, VCR 2, VCR 3 so that the buttons
on the switcher will also go VCR 1, VCR2, VCR3.
The real world conspires mightily against convention. If you have
four cameras, but only two feed directly into the switcher, what
do you do --- do you draw your cameras in order 1, 2, 3, 4, then
list them in the patch bay in order, but then split the switcher
inputs so that the patch bay has input 1, input 2, and for the
third and fourth outputs to the patch bay, leave them blank or
put something else there? This forces switcher inputs 3 and 4
to be split further away from 1 and 2 on the bay, a lesion in
logic. On the other hand, you could have the switcher inputs listed
1, 2, 3, 4 but across from them on the bay's input side, you would
camera 1, camera 2, something else, something else, forcing cameras
3 and 4 to be split from 1 and 2. There is no way to make these
situations work out perfectly; just decide what will make the
most sense to you. I tend to group my cameras and other devices
in logical order, allowing switcher and mixer inputs to be split
up, but at least I keep them in sequential order, even if there
are gaps between.
I try to make the audio patch bays parallel the video patch bays
so that once you've made a video patch, you can find the audio
patch quickly. An army of Murphy's Laws attack this plan as well.
Stereo audio requires twice as many sockets as video, which means
that video sources 1 through 11 take up video sockets 1 through
11 while taking up audio sockets 1 through 22. Further, video
involves much more processing than audio. I somehow have to work
time base correctors, proc amps, monitors, distribution amplifiers,
and other paraphernalia into the video patch bay and have very
few similar devices to put in the audio patch bay. I still try
to build them parallel even though I know I can't. If you have
the luxury of extra patch bays so that you can leave some sockets
empty, you may be able to construct your audio and video patch
bays in a half-parallel fashion. For instance, you might display
11 video sources, leaving 11 sockets empty so that the corresponding
audio patch bay can be filled with exactly the same sources. If
this method seems too wasteful to you, consider putting some of
the video processing equipment (for which there is no audio counterpart)
in the remaining 11 sockets on the source patch bay. This at least
fills up the patch bay while keeping the video processing equipment
grouped together.
Drawing the lines-
Once you have organized your sources, patch bays, monitors, and
switchers (or mixers), it is time to draw the lines between them.
I used to draw one line to connect every single item on the page.
This has ended up with lines of angel hair spaghetti, many of
them parallel, non of them easy to follow. A draftsman convinced
me that it was alright to group lines together if they were all
going to approximately the same place. Thus, ten sources would
have their lines joined together, perhaps travel to a patch bay,
then split out again for the patch bay. After the patch bay, some
lines would regroup to a single line and travel to a switcher
where they split again.
In order to trace which line goes where, each one needs a name.
Every line, before it joins a group, gets little flag telling
where it is going. If VCR2 feeds patch bay input R14, then its
line gets flag listing R14 as its destination. At the patch bay
end, no flag is necessary because the patch bay already lists
VCR2 as the source. Similarly, switcher input #1 which might be
camera #1, gets a flag on its line showing that the line comes
from patch bay K, position #1. Thus, all the wires, even if grouped
together, can be traced from their source to their destination.
When connecting the actual wires, each gets a label on the end
telling where it's going. In most cases, the label reads the same
as the flag on the diagram.
Some wires connect to other rooms, which in turn have their own
wiring diagrams. To avoid cramming too much onto one diagram,
simply flag these lines with an arrow indicating their destination
on the next diagram.
Surprises uncovered -
What happens when you feed the Y/C output from a VCR to a compatible
Y/C TBC, to another VCR or a switcher? If the signals are travelling
as Y/C, they require a special connector. How do you put that
in the patch bay? One solution is to purchase or make a breakout
connector which separates the Y/C wires into separate coax wires.
These each get their own terminal on the patch bay. Now you will
be able to patch Y/C signals between various sources and processing
devices. Just make sure your patch cables are the same length
or else the C might not arrive at the same time as the Y.
On the audio side, consider how many of your devices use balanced
lines (3-prong XLR connectors), versus unbalanced lines (RCA,
mini, or phono connectors). Balanced and unbalanced equipment
do not like to be connected directly together. In order to take
advantage of balanced line's better signal characteristics, a
balancing transformer is needed. This should show up in the diagram
somewhere.
It would be wise to convert all inputs and outputs to balanced
or unbalanced lines so that users wouldn't accidentally patch
from one to the other. The same is true for high and low level
signals. Distortion can occur if an unsuspecting user were to
patch a high level source into a low level input.
On the video side, it is good to keep RF (radio frequency) and
video signals separate. Antenna, TV cable, and modulated video
signals should not be patched directly to video equipment. Keeping
the RF inputs and outputs on a separate patch bay or a separate
section of the patch bay, and perhaps color coding the patch bay
labels will help keep these signals kosher.
Labeling wires and buttons -
Unlabeled buttons, sockets, and wires are close to useless. Every
wire should have a flag attached to each end. Every button should
tell what it does, and every socket should tell where it feeds.
The wiring diagram is helpful here too. Once you have selected
formal names for your sources, patch bay legends, and labeled
the lines as they emerged from groups in the drawing, you have
everything you need to make logical labels on the wires and equipment
itself. The wires could either list what item they are feeding
to or from, or could list the patch bay number that they connect
to, or could simply have an accession number (a serially selected
number that doesn't mean anything except to designate an identity
for the wire). If such serial numbers are used, they should be
listed on the wiring diagram also so that the cables can be easily
traced.
Naming the switches and sockets the same as they are named on
the wiring diagram simplifies the process of referring back and
forth between the diagram and the real world.
Separation of labor -
Making wiring diagrams is tedious and takes a lot of thought,
but it is something the average, intelligent audio or video person
can do. Engineering firms charge thousands of dollars to create
these diagrams, and if your time is very expensive, maybe this
is a good deal. Even if your time is expensive, the thinking that
goes into the first version of these diagrams is productive work;
you need to do a lot of soul searching about how you want your
system to operate, what is its default state (what happens when
there are no patches, and everything simply gets turned on) should
be. As you develop your diagrams, you learn more about the flexibility
of your system and may discover interconnections you hadn't thought
of before. You may also discover problems about sychronization,
timing, cable length, and signal distribution. You will quickly
learn how many distribution amplifiers you will need to buy if
you are sending signals to several places. Many a policy in this
world has changed when the boss had to sit down and actually write
it. That's when he finally discovered how foolish it appeared,
once in print. Wiring diagrams are very instructive.
After creating your rough diagram, you can:
1. Redraw it neatly on a large piece of paper.
2. Get someone else to redraw it neatly on a large piece of paper.
3. Enter it into a computer and have the CPU redraw the diagram.
Professional draftspeople can do a neat job of reorganizing your
schematic spaghetti into a neat package. Since the thinking has
already been done, these people do not have to be experts in your
field, making their services somewhat affordable (as opposed to
having an engineering firm do the drawings). Similarly, when the
time comes to label the wires, buttons, and sockets, a moderately
paid person with neat handwriting could be employed. The diagram
tells all; the labeling becomes a mechanical job.
If you have access to large photocopiers or blueprint making equipment,
you could create your wiring diagram on a large single sheet.
If you do not have access to this equipment, you might consider
creating your diagram on a matrix of 8-1/2 x 11 sheets. The sheets
would be easy to photocopy and could then be taped or mounted
together into a larger display. If one part of the facility changed,
you would only need to update one page of the master, photocopy
it, and stick the photocopy where the old page used to be.
I like to mount my diagrams onto foamcore, perhaps putting the
video wiring on one side and the audio wiring on the other. The
foamcore could then be slipped behind the console or hung on the
wall for easy reference.
I am a neat freak. I am compulsive about having drawers, switches,
and sockets neatly labeled. Some people can quickly find things
in a messy pile, but I cannot (I often cannot even find things
when they are neatly filed). I desperately need wiring diagrams
when troubletracing. Further, I am too impatient to read all the
lettering on a patch bay to find the socket that I want; I love
zipping over to the wiring diagram to track my way down to the
appropriate socket, and then look for it on the patch bay. If
you are like Felix Unger and I, there are wiring diagrams in your
future. If not, never ask the likes of me to help you fix anything;
spaghetti is for eating, not for untangling and tracing.
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