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Terminal layout is arrangsa.
~n
thci console to allow adequate
separation of cablss up to the point of connectlng to the ter-
minal blocks.
Low level microphone cables connect on the left
to TBl.
Medium .level cables connect in the, cent8r to TB3.
High
level cables connect to TB4 and (in the rear) to TB6.
Intercom
"Tiring conn8ctions are brought out to TB6 since these are auxil.-·
iary circuits which may vary in level from -·50 DB to
+28
DBN.
The speaker outllUt cables are hi.gh level and should not be run
with low level cables.
Conduit generally affords enough shielding so that different
levels in separate condui.t presents no isolati.on problem sven
wi thout spaci.ng them apart.
liicrophone level condui t and
speaker level conduit can probably run along tog8ther with no
crosstalk.
HovlBvor, if practical, it is advisable to maintain
physical separation and add to the safety of the installation.
Fower Circuits, especially those with high current, should not
be in close proximi ty "lith program carrying conduit; elec tro-
mag'letic shielding is poor in most conduit.
Grounding circuits, like cable layout and most systems work
methods, are unpredictable to a certain extent.
Therefore, no
hard and fast rules apply 100% of t;he time.
In this section it
is attempted to cover the things to avoid and to present gener-
ally accepted. :practices tbat always give good J.:esul ts,
Ol-'
all.cv;
good results to be obtained ,vi -eh minor modii ication,
Entir'ely
dif ferent approaches have been used, some with good results, but
unless you are an expert on the subject, most are risky.
The console grounding system i.s based on the one point ground.
Different circuit grounds are insulated from the chassis and
other grounds except at one point, where they all join together
and go to earth ground.
This system .prevents multiple ground
loops vii th the result ing hum pickup from Circulating currents
~nd l~F
pickup and regeneration •
. External circuits connected in the console should not destroy
this system.
Microphone circuits are not grounded in the con--
sole.
The shi.elds should not be grounded externaLly except after
noise checks.
They may then be grounded if better results are
obtained.
'rurntable and. tape inputs are unbalanced and the
common side is grounded.
If the inputs are unbalanced, the
common side should connect to the back row of the terminal
blocks (IB, 2B, 3B, etc.).
If the input circui.t is grounded
external to the console, the ground should be
1
if ted if pos-"
sible to prevent ground loops.
If the ground cannot be re-·
moved, or if tho circui.t impedance ,"111 not match the 600 ohm
input, a matching transformer should be used.
Order Gates
A·-21
line matching and isolation transformer.
The Executive
6/26/62
-4·-
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