Studio Technologies 42 - Manual (Page 14)

Model 42 User Guide Issue 1, July 2004
Studio Technologies, Inc. Page 15
user devices. This allows more devices
to be supported over longer cable runs.
How does the Model 42 accomplish
this? Simply by having circuitry that
is superior to that used in most of the
“industry-standard” equipment. In most
IFB interface devices, an adjustable volt-
age regulator integrated circuit is used
as a combination of audio modulator and
current limiter. While this is a simple and
inexpensive solution, it’s not without sig-
nificant limitations. The major problem
with this method is the type of voltage-
current “knee” that is created. As the load
current increases past about 50% of the
rated maximum the output voltage begins
to decrease. This means that the usable power delivered to the connected
device(s) will start to drop well before
the rated output is reached. This limitation
will become significant in applications
that use long cable runs. As the IFB circuit
voltage begins to drop problems with user
device performance can occur. Contrast
this situation with the performance pro-
vided by the Model 42. The DC voltage
supplied by its IFB circuits won’t “poop
out” when loaded over its 0 to 200 milli-
amperes range. This will allow IFB belt
pack and announcer’s console devices to
work correctly in many more applications.
Figure 3 shows the IFB circuit voltage-
current curves for the RTS 4000-series and
the Model 42 Interface. The performance
differences are quite interesting.
Figure 3. IFB Circuit Voltage-Current Curves for RTS 4000-Series and Model 42 Interface
0
5
10
15
20
25
30
35
0 50 100 150 200 250
Current (mA)
Vol
tage (
V
)
4010
Model 42