Studio Technologies 93 - Manual (Page 16)

Issue 1, January 2008 Model 93 User Guide
Page 16 Studio Technologies, Inc.
will show the pin or pins that are connected
to the pin selected for testing. Repeat test-
ing of the cable, when in channel mode, or
the specific pin, when in the pin mode, will
take place. The displayed results will refresh
with each test cycle.
Master/Slave Mode Operation
A challenge is encountered when testing
cable assemblies where both ends can’t
be physically connected to one Model 93.
This occurs in cases such as where W1s
are permanently installed in stadiums and
arenas, or when portable cabling has been
“run” and can’t be accessed easily. Using
two Model 93 units, virtually any W1 cable
assembly, fan out, or even 3-pin XLR cables
can be tested.
The master/slave mode is created in the
Model 93’s hardware and software so that
the unit’s functions are “split” into a send-
test-signals portion and a receive-test-
signals portion. A communications link is
established between two Model 93 units,
allowing the two functions, send and re-
ceive, to work together. The data passing
in each direction on the data link effectively
“couples” the two Model 93 units into one.
One unit is designated as “master” and
coordinates the activities of a test. The
“slave” unit follows the commands of the
master, performing the actions requested
and returning test results as required.
Master/slave testing operation is quite easy
to initiate and use. But the flexibility pro-
vided by the Model 93’s multiple operating
modes can be a bit tricky to get one’s head
around. While this user guide will document
the basic “hows and whys” of master/slave
operation, only experience can serve as the
best teacher. It’s recommended that some
“bench” experimentation be done prior to
going full bore out in the field.
Master/Slave Data Link
For two Model 93 units to be used in a
master/slave arrangement they must be
interconnected with a 2-conductor signal
path. This connection is referred to as the
master/slave data link. It supports the trans-
mission of bi-directional serial data as well
as linking the power supply common con-
nections of both units. A BNC connector
is used for the master/slave data link. This
type of connector was selected not because
of a specific technical requirement, but be-
cause of its wide popularity in the broadcast
and video industry. In many applications
where W1 cable assemblies are to be tested
there will also be BNC-terminated video ca-
bles present. This will most likely allow the
easier method of interconnecting two Model
93 units. However, there’s no reason that
other types of cable can’t be used. Options
can include shielded microphone cable and
twisted pair telephone cable. While using
coax will allow the greatest distance be-
tween Model 93 units, even twisted pair has
been tested at over 4000 feet! This should
be well in excess of the length of any W1
cable assembly that needs to be tested.
It’s important to note that two metallic con-
nections must be made between the master
and slave Model 93 units. When using a
coaxial cable the two metallic connections
would consist of the inner conductor and
the shield. Alternately pins 2 and 3 of a
standard audio cable that uses XLR connec-
tors would serve the purpose. However, any
transformers, “baluns,” or capacitors in the
connection path that provide DC isolation
will prevent master/slave operation.
After interconnecting two Model 93 units, it’s
quite easy to confirm that the master/slave
data link has been established. Temporarily
designate one of the units as slave. Be sure
that it is powered down. Turn on the other