Manual

Model 45DC User Guide Issue 3, March 2016
Studio Technologies, Inc. Page 7
remain stable. This unique feature makes
certain that objectionable audio signals,
including oscillations and “squeals,” won’t
be sent to other Dante-enabled devices.
A significant capability of the Model
45DC’s two party-line intercom interfaces
is their ability to supply DC power and
200 ohm AC terminations to “create” two
independent intercom circuits. The 28 volt
DC output can power user devices such
as beltpacks. With up to 150 milliamperes
(mA) of current available, a typical enter-
tainment application could connect up to
three RS-501 or five RS-701 beltpacks to
each of the Model 45DC’s two interfaces.
In many applications this can eliminate the
need for an external intercom power sup-
ply, thereby reducing total system cost,
weight, and required mounting space. The
power supply outputs are monitored for
over-current and short-circuit conditions.
Under firmware (embedded software)
control the outputs will automatically cycle
off and on to help prevent damage to the
circuitry and connected equipment.
Dante Audio-over-Ethernet
Audio data is sent to and from the Model
45DC using the Dante Audio-over-Ethernet
media networking technology. Audio
signals with a sample rate of 48 kHz and
a bit depth of up to 24 are supported.
Audio receiver (input) and transmitter
(output) channels on associated Dante-
enabled devices can be assigned to the
Model 45DC using the Dante Controller
software application. This makes selecting
the way in which a Model 45DC fits into a
specific application a simple matter.
Analog Hybrids with Auto
Nulling
Two circuits referred to as “hybrids” inter-
face the Dante input and output channels
with the two party-line interface channels.
The hybrids provide low noise and dis-
tortion, good frequency response, and
high return-loss (“nulling”), even when
presented with a wide range of party-line
conditions. Unlike telephone-line (“POTS”)
oriented DSP-based hybrid circuits, the
Model 45DC’s analog circuitry maintains
extended frequency response. With a
passband of 100 Hz on the low end and
8 kHz on the high end, natural-sounding
voice signals can be sent to and received
from a party-line circuit.
The Model 45DC’s sophisticated hybrid
auto nulling function uses a combination
of digital and analog circuitry under micro-
processor control to achieve significant
trans-hybrid loss. This return-loss “null” is
achieved by making a series of firmware-
directed adjustments to account for the
resistive, inductive, and capacitive condi-
tions that are present on the connected
party-line cabling and user devices. When-
ever one of the Model 45DC’s auto null
buttons is pressed digital circuitry adjusts
the associated hybrid to achieve its maxi-
mum return-loss in less than 15 seconds.
While the nulling process is automatic, it
only takes place upon user request. The
resulting null parameters are stored in
nonvolatile memory.
Pro Audio Quality
The Model 45DC’s audio circuitry was
designed in the spirit of professional
audio equipment rather than that found
in typical party-line intercom gear. High-
performance components are used