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Systems Engineering 13-27

•

Verifying system capability

•

Verifying system performance

•

Maintaining the system baseline

•

Forming an analytical framework for further analysis

Depending on the complexity of the new installation, the systems engineer may have to pro-

vide orientation and operating instruction to the users. During the operational support phase, sys-
tem engineers:

•

Receive input from users

•

Evaluate proposed changes to the system

•

Establish their effectiveness

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Facilitates the effective incorporation of changes, modifications, and updates

Depending on the size of the project and the management organization, the systems engi-

neer's duties will vary. In some cases the systems engineer may have to assume the responsibili-
ties of planning and managing smaller projects.

13.1.4 References

1.

Hoban, F. T., and W. M. Lawbaugh: Readings In Systems Engineering, NASA, Washington,
D.C., 1993.

2.

System Engineering Management Guide, Defense Systems Management College, Virginia,
1983.

13.1.5 Bibliography

Delatore, J. P., E. M. Prell, and M. K. Vora: “Translating Customer Needs Into Product Specifi-

cations”, Quality Progress, January 1989.

DeSantis, Gene: “Systems Engineering Concepts,” in NAB Engineering Handbook, 9th ed.,

Jerry C. Whitaker (ed.), National Association of Broadcasters, Washington, D.C., 1999.

DeSantis, Gene: “Systems Engineering,” in The Electronics Handbook, Jerry C. Whitaker (ed.),

CRC Press, Boca Raton, Fla., 1996.

Finkelstein, L.: “Systems Theory”, IEE Proceedings, vol. 135, Part A, no. 6, July 1988.

Shinners, S. M.: A Guide to Systems Engineering and Management, Lexington, 1976.

Tuxal, J. G.: Introductory System Engineering, McGraw-Hill, New York, N.Y., 1972.

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Systems Engineering

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Systems Engineering

13-29

Chapter

13.2

Engineering Documentation

Fred Baumgartner, Terrence M. Baun

13.2.1 Introduction

Video facilities are designed to have as little down-time as possible. Yet, inadequate documenta-
tion is a major contributor to the high cost of systems maintenance and the resulting widespread
replacement of poorly documented facilities. The cost of neglecting hours of engineering docu-
mentation is paid in weeks of reconstruction.

Documentation is a management function every bit as important as project design, budgeting,

planning, and quality control; it is often the difference between an efficient and reliable facility
and a misadventure. If the broadcast engineer does not feel qualified to attempt documentation
of a project, the engineer must at the very least oversee and approve the documentation devel-
oped by others.

Within the last few years the need for documentation has increased with the complexity of the

broadcast systems. Fortunately, the power of documentation tools has kept pace.

13.2.2 Basic Concepts

The first consideration in the documentation process is the complexity of the installation. A
basic video editing station may require almost no formal documentation, while a large satellite or
network broadcast facility may require computerized databases and a full time staff doing noth-
ing but documentation updates. Most facilities will fall somewhere in the middle of that spec-
trum.

A second concern is the need for flexibility at the facility. Seldom does a broadcast operation

get “completely rewired” because the cabling wears our or fails. More often, it is the supporting
documentation that has broken down, frustrating the maintainability of the system. Retroactive
documentation is physically difficult and emotionally challenging, and seldom generates the
level of commitment required to be entirely successful or accurate; hence, a total rebuild is often
the preferred solution to documentation failure. Documentation must be considered a hedge
against such unnecessary reconstruction.

Finally, consider efficiency and speed. Documentation is a prepayment of time. Repairs,

rerouting, replacements, and reworking all go faster and smoother with proper documentation. If

Source: Standard Handbook of Audio and Radio Engineering

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13-30 Standards and Practices

your installation is one in which any downtime or degradation of service is unacceptable, then
budgeting sufficient time for the documentation process is critically important.

Because, in essence, documentation is education, knowing “how much is enough” is a diffi-

cult decision. We will begin by looking at the basics, and then expand our view of the documen-
tation process to fit specialized situations.

13.2.2a

The Manuals

Even if you never take a pen to paper, you do have one source of documentation to care for, since
virtually every piece of commercial equipment comes with a manual.

Place those manuals in a centralized location, and arrange them in an order that seems appro-

priate for your station. Most engineering shops file manuals alphabetically, but some prefer a fil-
ing system based on equipment placement. (For example, production studio equipment manuals
would be filed together under a “Production Studio” label and might even be physically located
in the referenced studio.) But whatever you do, be consistent Few things are as frustrating to a
technician as being unable to locate a manual when needing something as simple as a part num-
ber or the manufacturer’s address.

Equipment manuals are the first line of documentation and deserve our attention and respect.

13.2.2b

Documentation Conventions

The second essential item of documentation is the statement of “conventions.” By this we mean a
document containing basic information essential to an understanding of the facility, posted in an
obvious location and available to all who maintain the plant. Consider the following examples of
conventions:

•

Where are the equipment manuals and how are they organized?

•

What is the architecture of the ground system? Where is the central station ground and is it a
star, grid, or other distribution pattern? Are there separate technical and power grounds? Are
audio shield grounded at the source, termination, or both locations?

•

What is the standard audio input/output architecture? Is this a +8 dBm, +4 dBm, or 0 dBm
facility? Is equipment sourced at 600 

Ω terminated at its destination, or left unterminated?

Are unbalanced audio sources wired with the shield as ground or is the low side of a balanced
pair used for that purpose? How are XLR-type connectors wired—pin 2 high or low?

•

How can a technician disconnect utility power to service line voltage wiring within racks?
Where are breakers located, and how are they marked? What equipment is on the UPS power,
generator, or utility power? Whom do you call for power and building systems maintenance? 

•

Where are the keys to the transmitter? Is the site alarmed? 

For such an essential information source, you will find it takes very little time to generate the

conventions document. Keep it short—it is not meant to be a book. A page or two should be suf-
ficient for most installations and, if located in a obvious place, this document will keep the tech-
nical staff on track and will save service personnel from stumbling around searching for basic
information. This document is the key to preventing many avoidable embarrassments.

The next step beyond the conventions document is a documentation system. There are three

primary methods:

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Engineering Documentation

Engineering Documentation 13-31

•

Self documentation

•

Database documentation

•

Graphic documentation

In most cases, a mixture of all three is necessary and appropriate. In addition to documenting

the physical plant and its interconnections, each piece of equipment, whether commercially pro-
duced or custom made, must be documented in an organized manner. 

Self Documentation

In situations where the facility is small and very routine, self documentation is possible. Self
documentation relies on a set of standard practices that are repeated. Telephone installations, for
example, appear as a mass of perplexing wires. In reality, the same simple circuits are simply
repeated in an organized and universal manner. To the initiated, any telephone installation that
follows the rules is easy to understand and repair or modify, no matter where or how large. Such
a system is truly self documenting. Familiarity with telephone installations is particularly useful,
because the telephone system was the first massive electronic installation. It is the telephone sys-
tem that gave us “relay” racks, grounding plans, demarcation points, and virtually all of the other
concepts that are part of today’s electronic control or communications facility.

The organization, color codes, terminology, and layout of telephone systems is recorded in

minute detail. Once a technician is familiar with the rules of telephone installations, drawings
and written documentation are rarely required for routine expansion and repair. The same is true
for many parts of other facilities. Certainly, much of the wiring in any given rack of equipment
can be self documenting. For example, a video tape recorder will likely be mounted in a rack
with a picture monitor, audio monitor, waveform monitor, and vectorscope. The wiring between
each of these pieces of equipment is clearly visible, with all wires short and their purpose obvi-
ous to any technician familiar with the rules of video. Furthermore, each video cable will con-
form to the same standards of level or data configuration. Additional documentation, therefore,
is largely unnecessary.

By convention, there are rules of grounding, power, and signal flow in all engineering facili-

ties. In general, it can be assumed that in most communications facilities, the ground will be a
star system, the power will be individual 20 amp feeds to each rack, and the signal flow within
each rack will be from top to bottom. Rules that might vary from facility to facility include color
coding, connector pin outs, and rules for shield and return grounding.

To be self documenting, the rules must be determined and all of the technicians working on

the facility must know and follow the conventions. The larger the number of technicians, or the
higher the rate of staff turn-over, the more important it is to have a readily available document
that clearly covers the conventions in use.

One thing must be very clear: a facility that does not have written documentation is not auto-

matically self documenting. Quite the contrary. A written set of conventions and unfaltering
adherence to them are the trade marks of a self documenting facility.

While it is good engineering practice to design all facilities to be as self documenting as pos-

sible, there are limits to the power of self documentation. In the practical world, self documenta-
tion can greatly reduce the amount of written documentation required, but can seldom replace it
entirely.

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Engineering Documentation