User Guide
Issue 1, September 2014
This User Guide is applicable for serial numbers
M45DR-00151 and later
Copyright © 2014 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50015-0914, Issue 1
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Table of Contents
Introduction ................................................................... 5
Installation ..................................................................... 9
Configuration ................................................................ 12
Operation ...................................................................... 13
Technical Notes ............................................................. 18
Specifications ................................................................ 21
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Issue 1, September 2014 Model 45DR User Guide
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Introduction
The Model 45DR Dante™ to 2-Channel
Party-Line Intercom Interface is designed
for applications that utilize 2-channel analog party-line (PL) intercom technology.
This type of intercom is commonly used
in broadcast, corporate, and commercial
applications where a simple, reliable, easy
to use solution is desired. The RTS® TWSeries of 2-channel intercom equipment is
directly compatible with the Model 45DR.
The Dante Audio-over-Ethernet media
networking technology is used to transport the two send and two receive audio
channels associated with the party-line
circuit. Two hybrid circuits with automatic
nulling provide excellent audio quality and
high return-loss. (These hybrid circuits are
sometimes referred to as 2-wire to 4-wire
converters.) The Model 45DR is compatible with the latest broadcast and audio
equipment that uses Dante technology. An
Ethernet connection is all that’s required
to make the Model 45DR part of a sophisticated, networked audio system.
A Model 45DR can interconnect with
devices such as matrix intercom systems,
DSP processors, and audio consoles. The
Model 45DR is directly compatible with the
RTS ADAM® OMNEO® matrix intercom
network. Alternately, two Model 45DR units
can interconnect by way of the associated
Ethernet network. The Model 45DR can
be powered by Power-over-Ethernet (PoE)
or an external source of 12 volts DC. A
party-line power source and impedance
termination networks can be supplied by
the Model 45DR, allowing connection of
user beltpacks such as the popular RTS
BP325. A Model 45DR can also connect
with an existing powered and terminated
intercom circuit. Audio level meters provide confirmation of system performance
Figure 1. Model 45DR standard “throw-down” front view
Figure 2. Model 45DR back view
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during setup and operation. Standard connectors are used for party-line intercom,
Ethernet, and DC power interconnections.
The Model 45DR’s enclosure has a “1/2rack” 1U form factor and weighs less than
two pounds, making it well suited for use
in portable applications. Alternately, using
one of the optional rack-mount front panels, one or two Model 45DR units can be
mounted in a single space (1U) of a standard 19-inch rack enclosure.
Applications
There are two main ways that the Model
45DR can be used in applications: adding
party-line intercom support for matrix intercom systems and linking two stand-alone
party-line intercom circuits. Ports on matrix
intercom systems that support Dante, such
as the RTS ADAM with OMNEO, can be
routed to the Model 45DR’s Dante input
(receiver) and output (transmitter) channels. The Model 45DR’s circuitry will then
convert these signals into a 2-channel
party-line intercom circuit. In this way adding party-line support to RTS + OMNEO is
a simple task. The Model 45DR can also
be used with matrix intercom systems that
don’t support Dante. An external analogto-Dante interface can be used to convert
analog intercom ports to Dante channels.
Once in the digital domain, these Dante
channels can be interconnected with the
Model 45DR’s audio input and output
channels.
Two separate party-line intercom circuits
can easily be interconnected using two
Model 45DR Interfaces. A Model 45DR is
connected to each party-line circuit as well
as the Dante network. The Dante Controller software application will then be used to
route the audio channels between the two
units. That’s it — nothing else is required
to achieve excellent performance.
The Model 45DR can also be used to
“bridge” a 2-channel party-line intercom
circuit with one or two single-channel
party-line intercom circuits. This involves
using a Model 45DR with the 2-channel
circuit and one or two of the Studio Technologies Model 45DC Intercom Interface
units with the single-channel circuits. The
Model 45DC is the “cousin” of the Model
45DR and supports two single-channel
party-line intercom circuits rather than one
2-channel circuit. These single-channel
circuits, typically supported by equipment
from Clear-Com®, are commonly used in
theatrical and entertainment applications.
Party-Line Interface
The Model 45DR’s party-line intercom
interface is optimized for connection with
2-channel party-line intercom circuits and
user devices such as the TW-Series from
RTS. In addition, other industry-standard
single- and 2-channel party-line intercom
circuits and user devices, including those
from Clear-Com®, are compatible. (While
the Model 45DR will function in a limited
manner with single-channel Clear-Com
circuits, the Model 45DC Intercom Interface is the much-preferred choice for
that.) A party-line active detection function
ensures that should a user beltpack or
active party-line circuit not be connected
the Model 45DR’s interface circuitry will
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
45DR’s party-line interface is its ability
to supply DC power and 200 ohm AC
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terminations to “create” an intercom circuit.
The 29 volt output can power a moderate
number of devices such as beltpacks. With
up to 240 milliamperes (mA) of current
available, a typical broadcast application
which uses two or three BP325 beltpacks
can be supported. In many applications
this can eliminate the need for an external intercom power supply, reducing total
system cost, weight, and required mounting space. The power supply output is
monitored for over-current and short-circuit
conditions. Under software control the
output 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
45DR 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 input (receiver) and output (transmitter) channels on associated Dante-enabled
devices can be assigned to the Model
45DR using the Dante Controller application. This makes it simple to select the way
in which a Model 45DR fits into a specific
application.
Analog Hybrids with Auto
Nulling
Circuits referred to as “hybrids” interface
the Dante input and output channels with
the two party-line channels. The hybrids
provide low noise and distortion, good
frequency response, and high return-loss
(“nulling”), even when presented with a
wide range of party-line conditions. Unlike
telephone-line (“POTS”) oriented DSPbased hybrid circuits, the Model 45DR’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 partyline circuit.
The Model 45DR’s sophisticated hybrid
auto nulling function uses a combination
of digital and analog circuitry under microprocessor control to achieve significant
trans-hybrid loss. This return-loss “null” is
achieved by making a series of softwaredirected adjustments to account for the
resistive, inductive, and capacitive conditions that are present on the connected
party-line cabling and user devices. Whenever the Model 45DR’s auto null button is
pressed, digital circuitry adjusts the hybrids
to achieve their maximum 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 non-volatile memory.
Pro Audio Quality
The Model 45DR’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 throughout,
providing low-distortion, low-noise, and
high headroom. Using active filters the
frequency response of the audio channels
is limited to nominally 100 Hz to 8 kHz.
This range was selected to provide excellent performance for human speech while
maximizing the ability of the hybrid circuits
to create substantial “nulls.” Moreover,
the Model 45DR’s party-line intercom
power source offers a unique level of
performance; its ability to deliver power
while maintaining audio quality is simply
unmatched.
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Audio Meters
The Model 45DR contains two sets of
5-segment LED level meters. Each set of
two meters displays the level of the signals
being sent to and received from a party-line
interface channel. At the time of installation and setup the meters are invaluable in
helping to confirm correct operation. During normal operation the meters offer rapid
confirmation of audio signals flowing in to
and out of the unit. Additional LED indicators are also provided on the front panel,
offering a status indication of the party-line
DC power source, party-line activity status,
and the auto null functions. Two other LEDs
offer a direct indication of what source is
powering the Model 45DR.
Ethernet Data, PoE, and DC
Power Source
The Model 45DR connects to a data network using a standard 100 Mb/s twistedpair Ethernet interface. The physical
interconnection is made by way of a Neutrik® etherCON RJ45 connector. While
compatible with standard RJ45 plugs,
etherCON allows a ruggedized and locking
interconnection for harsh or high-reliability
environments. The Model 45DR’s operating
power can be provided by way of the Ethernet interface using the Power-over-Ethernet (PoE) standard. This allows fast and
efficient interconnection with the associated
data network. To support PoE power management, the Model 45DR’s PoE interface
reports to the power sourcing equipment
(PSE) that it is a class 3 (medium power)
device. The unit can also be powered using
an external source of 12 volts DC.
For redundancy, both power sources can
be connected simultaneously. An internal
switch-mode power supply ensures that all
Model 45DR features, including party-line
intercom circuit power, are available when
the unit is powered by either source. Four
LEDs on the back panel display the status
of the network connection, Dante interface, and PoE power source.
Simple Installation
The Model 45DR uses standard connectors to allow fast and convenient interconnections. An Ethernet signal is connected
using a Neutrik etherCON RJ45. If Powerover-Ethernet (PoE) is available operation
will commence immediately. An external
12 volt DC power source can also be connected by way of a 4-pin XLR. Party-line
intercom connections are made using
3-pin male and female XLR connectors.
The Model 45DR is housed in a rugged
yet lightweight aluminum enclosure that
is designed to be “field tough.” It can be
used as a standalone portable unit, supporting what’s known in the broadcast
world as “throw-down” applications.
Rack-mount options are also available
allowing one or two units to be mounted
in one space (1U) of a standard 19-inch
rack enclosure.
Future Capabilities and
Firmware Updating
The Model 45DR was designed so that its
capabilities can be enhanced in the future.
The primary additions will be in the area of
Dante remote control transport functionality. Should an industry-standard be established it’s expected that remote control
and status transport of the auto null, call
light, and microphone mute functions will
be available. (The Model 45DR’s circuitry
includes provisions for detecting and
generating RTS TW “call light” and “mic
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kill” signals.) A USB connector, located on
the Model 45DR’s back panel, allows the
operating firmware (embedded software)
to be updated using a USB flash drive. To
implement the Dante interface the Model
45DR uses Audinate’s Ultimo™ integrated
circuit. The firmware in this integrated
circuit can be updated via the Ethernet
connection, helping to ensure that its
capabilities remain up to date.
Installation
In this section signal interconnections will
be made using the connectors located on
the back panel of the Model 45DR. Connections to one or more party-line user
devices or an existing party-line intercom
circuit will be made using one of the 3-pin
XLR connectors. An Ethernet data connection will be made using either a standard
RJ45 patch cable or an etherCON protected RJ45 plug. A 4-pin XLR connector allows the connection of an external source
of 12 volts DC.
System Components
Included in the shipping carton are the
Model 45DR Intercom Interface and a user
guide. If a rack-mount front panel is going
to be used as part of the installation it will
typically be shipped in a separate carton.
If the installation or specific application
requires an external source of 12 volts DC
it needs to be provided separately. An applicable power supply, the Studio Technologies PS-DC-02, is available as an option.
Locating the Model 45DR
The location of the Model 45DR will depend on the length of the cable runs
needed to link the unit with the associated
party-line intercom devices. This type of
circuit carries unbalanced audio which can
be susceptible to interference and crosstalk issues. And since party-line intercom
circuits typically carry DC power a voltage
drop due to resistive loss can become an
issue. In general, minimizing the length
of the party-line intercom cables will help
ensure more reliable and consistent intercom system performance. Of equal importance is the 100-meter (325-foot) Ethernet
cable limitation. A final location criterion is
to ensure that access to the Model 45DR’s
front panel is available. An optimal location will allow convenient use of the auto
null pushbutton and easy observation of
the status and level meters LEDs.
Protecting the Enclosure
The Model 45DR is shipped as a selfcontained unit suitable for portable use
or placement in a semi-permanent location. Installed on the bottom of the chassis
are screw-on “bump on” protectors (also
known as “rubber feet”). These are useful
if the unit is going to be placed on surfaces where scratching of either the Model
45DR or the surface material could take
place. The “feet” can be removed, without
the use of a tool, when rack- or custommounting the unit.
Rack Mounting the
Model 45DR
For permanent or mobile applications it
might be desirable to mount one or two
Model 45DR units into one space (1U) of
a 19-inch rack enclosure. Two rack-mount
front panels, purchased separately, are
available from Studio Technologies. The
following provides details on how to install
and use the panels.
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To attach a Model 45DR unit to the singleunit rack-mount panel, begin the process
by using a 5/64-inch hex wrench to remove the four 4-40 thread hex-head machine screws that hold the standard front
panel to the chassis. Note that the screws
might be quite tightly affixed. Ensure that
a good-quality hex wrench is used and
press and hold it firmly while turning counterclockwise. Unless this recommendation
is followed the wrench can “cam out” and
the head could be “stripped.”
Using the screws that were just removed,
attach the rack-adapter front panel to the
Model 45DR’s chassis. To prevent damage
care is required when aligning the front
panel with the LEDs and auto null pushbutton switch that protrude through both
the Model 45DR’s chassis and front panel.
Tighten the four screws only after a careful
inspection ensures that the switch and all
26 of the LEDs protrude through the front
panel without interference. To allow vertical clearance in the associated rack, remove the four “bump on” protectors from
the bottom of the chassis. They are removed by using the fingers to rotate them
counter-clockwise; no tool is required.
Carefully protect and store the standard
front panel, along with the “bump on” protectors, for possible later use.
Mounting a Model 45DR to a dual-unit
rack-mount panel follows the same procedure but will apply to two units. Store both
of the removed standard front panels
and the eight “bump on” protectors for
possible later use. Note that on the rackpanels graphics the unit on the left is designated as A while the unit on the right is
designated as B. This is provided so that
each can be easily identified during installation, troubleshooting, and operation.
Once the desired one or two Model 45DR
units have been installed in a rack-mount
front panel, the assembly can be mounted
into the designated equipment rack. One
space (“1U” or 1.75 vertical inches) in
a standard 19-inch equipment rack is
required. Secure the front panel into the
equipment rack using two mounting screws
per side.
Ethernet Connection
An Ethernet connection that supports
100BASE-TX (100 Mb/s over twisted-pair)
is required for the Model 45DR’s Dante
Audio-over-Ethernet connectivity. A
10BASE-T connection is not sufficient for
Model 45DR operation. A 1000BASE-T
(“GigE”) connection is not supported unless
it can automatically “fall back” to 100BASETX operation. An Ethernet connection that
supports Power-over-Ethernet (PoE) is
preferred as it will provide operating power
for the Model 45DR. To support PoE switch
(PSE) power management the Model 45DR
will enumerate itself as a PoE class 3 device.
If PoE is not available an external 12 volt DC
power source can be connected. This will be
discussed later in this section of the guide.
The 100BASE-TX Ethernet connection is
made by way of a Neutrik etherCON protected RJ45 connector that is located on the
back panel of the Model 45DR. This allows
connection by way of a cable-mounted
etherCON plug or a standard RJ45 plug.
The Model 45DR’s Ethernet interface supports auto MDI/MDI-X so that most cabling
implementations will be correctly supported.
External 12 Volt DC Input
An external source of 12 volts DC can be
connected to the Model 45DR by way of a
4-pin male XLR connector which is located
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on the back panel. While the requirement
for the external source is to be nominally
12 volts, correct operation will take place
over a 10 to 18 volt range. The Model
45DR requires 1.0 amperes maximum for
correct operation. The DC source should
be terminated to a 4-pin female XLR connector with pin 1 negative (–) and pin 4
positive (+). Purchased as an option,
the PS-DC-02 power supply is available
from Studio Technologies. Its AC mains
input allows connection to 100-240 volts,
50/60 Hz and its 12 volt DC, 1.5 amperes
maximum output is terminated on a 4-pin
female connector.
As previously discussed in this guide, an
Ethernet connection that provides Powerover-Ethernet (PoE) can serve as the
Model 45DR’s power source. Alternately,
an external 12 volt DC source can be connected. For redundancy, both PoE and the
external 12 volt DC source can be connected at the same time. If both PoE and
an external 12 volt DC source are connected, power will be drawn only from the PoE
supply. If the PoE source becomes inoperative the 12 volt DC source will provide the
Model 45DR’s power with no interruption
in operation. (Of course, if both PoE and
Ethernet data support are lost that is
a very different situation!)
Party-Line Intercom
Connections
The Model 45DR’s party-line intercom
interface is designed to function in two
distinct ways. It can be connected to a
“powered” broadcast-standard 2-channel
party-line intercom circuit or directly
to party-line intercom user devices. A
2-channel party-line intercom circuit, such
as associated with TW-Series equipment
from RTS, has DC power and two audio
channels on a 3-pin XLR connector. Associated connectors are wired such that common is on pin 1 and 28 to 32 volts DC is on
pin 2. Channel 1 audio is superimposed on
the DC present on pin 2 while channel 2
audio is present on pin 3. Two impedancegenerating networks provide a 200 ohm
audio load from pin 2 to pin 1 and from pin
3 to pin 1. When the Model 45DR’s partyline interface is connected to an existing
intercom circuit it acts, from an audio
standpoint, as a standard user device. It
doesn’t draw (nor supply) any DC power.
The Model 45DR’s party-line interface can
also serve to create a “mini” 2-channel
intercom circuit. It provides a 29 volt DC
intercom power source and two 200 ohm
impedance generators, allowing a limited
number of 2-channel intercom user devices to be directly connected. The Model
45DR’s internal 29 volt DC power source
has a maximum current of 240 mA. This
moderate amount of power can be very
useful but does require that the type and
number of connected user devices be
selected appropriately. Many broadcast
applications use the popular RTS BP325
user beltpacks and the Model 45DR Intercom Interface can directly support up to
three of them. Wiring from the Model 45DR
intercom interface to the BP325 devices
requires that a 1-to-1, 2-to-2, 3-to-3 wiring
scheme on the 3-pin XLR connectors be
maintained.
For convenience, the party-line intercom
circuit or user devices can be connected
to the Model 45DR by way of a male or
female 3-pin XLR connector located on the
back panel. The two connectors are wired
in parallel (“multed”) and provide access
to the identical signals.
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Compatibility with Single-
Dante Configuration
Channel Intercom Systems
As previously discussed in this guide,
the Model 45DR is designed to support
2-channel party-line intercom circuits and
user devices. Applications that involve
single-channel party-line intercom circuits
and user devices (typically associated with
products from Clear-Com) can also be supported. These circuits and devices typically
utilize common on pin 1, power on pin 2,
and audio on pin 3. When connected to a
Model 45DR only channel 2 will be active;
channel 1 would not be utilized. A better
means to support these single-channel circuits and devices is to use the Studio Technologies Model 45DC Intercom Interface.
This unit, the “cousin” of the Model 45DR,
is optimized for single-channel party-line
intercom applications. Rather than providing a 2-channel interface the Model 45DC
provides two single-channel interfaces.
Detailed information about the Model 45DC
is available on the Studio Technologies,
Inc. website (www.studio-tech.com).
Configuration
Hardware Configuration
A 4-position DIP switch assembly, labeled
Configuration, is located on the Model
45DR’s back panel. The initial release of
the Model 45DR’s firmware (embedded
software) does not utilize any of these
switches. So unless something changes
in future firmware versions setting these
switches to either the off (down) or on (up)
positions has no impact.
To integrate the Model 45DR into an application a number of Dante-related parameters can be configured. At a minimum,
the audio input (receiver) and audio output (transmitter) channels must be routed.
The configuration settings will be stored
in non-volatile memory within the Model
45DR’s circuitry. The Model 45DR uses the
Ultimo 2-input/2-output integrated circuit
to implement the Dante architecture. This
dictates which parameters can be configured and what choices are available.
The audio input (receiver) and output
(transmitter) channels associated with
the Model 45DR’s Dante interface must
be assigned to desired sources and destinations. This will typically be done with
the Dante Controller software application
which is available for download free of
charge at www.audinate.com. Versions
are available to support Windows® and
OS X® operating systems. Within Dante
Controller a “subscription” is the term
used for routing a transmitter flow (a
group of output channels) to a receiver
flow (a group of input channels). Note that
as of the writing of this guide the Ultimo integrated circuit limits the number of Dante
flows to two in each direction (two transmitter and two receiver). These can either
be unicast, multicast, or a combination of
the two.
The Model 45DR has a default Dante
device name of ST-M45DR followed by a
unique suffix. The suffix identifies the specific Model 45DR that is being configured;
it relates to the MAC address of the unit’s
Ultimo integrated circuit. The Model 45DR
provides two Dante output (transmitter)
channels with the default names of
From PL Ch1 and From PL Ch2. The
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Model 45DR has two Dante input (receiver) channels with default names of
To PL Ch1 and To PL Ch2. Using Dante
Controller these names can be revised as
appropriate for the specific application.
The Model 45DR only supports an audio
sample rate of 48 kHz but does have the
ability to select a pull-up/pull-down value.
This value can be selected using the
Dante Controller application. The Model
45DR can serve as the clock master for
a Dante network but in most cases that
would not be optimal.
Model 45DR units will typically be used
in either of two configurations: “point-topoint” or in association with other Danteenabled equipment. The first configuration
finds two units working together to “link”
two physical locations. At each location
there will either be an existing party-line
intercom circuit or a set of user devices.
The two Model 45DR units will be operating “point-to-point,” interconnected by
way of the associated Ethernet network.
For this application the audio routing
would be very simple. To PL Ch1 on each
unit would be routed to From PL Ch1 on
the other unit. And To PL Ch2 on each
unit would be routed to From PL Ch2 on
the other unit.
the OMNEO card. Other equipment that
supports Dante, such as audio consoles
or audio interfaces (Dante-to-MADI, Danteto-SDI, etc.), can have their audio channels routed to and from a Model 45DR.
Operation
At this point the Model 45DR should have
its party-line and Ethernet connections
made. Depending on the application an
external 12 volt DC power connection may
have also been made. The Dante input
(receiver) and output (transmitter) channels should have been routed using the
Dante Controller software application.
Normal operation of the Model 45DR can
now begin.
Initial Operation
The Model 45DR will begin its initial functioning a few seconds after its power
source is connected. As previously discussed, the power source can be provided by Power-over-Ethernet (PoE) or an
external source of 12 volts DC. If both are
connected the PoE source will power the
unit. Should PoE subsequently no longer
be available, operation will continue using
the external source.
The other typical applications will have
one Model 45DR connected to an existing
party-line intercom circuit or supporting
a set of user devices. The unit’s audio
channels would be routed to input and
output audio channels on associated
Dante-enabled equipment. For example,
the RTS ADAM matrix intercom system
provides Dante interconnection capability using its OMNEO interface card. The
audio channels on the Model 45DR would
be routed to and from audio channels on
Model 45DR User Guide Issue 1, September 2014
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Upon Model 45DR power up many of
the status and meter LEDs will activate in
test sequences. The PoE and USB LEDs,
located on the back panel, will light one
after another. On the front panel the input
power, channel status, and level meter
LEDs will light in a sequence. Once the
test sequences have completed two
columns of front-panel level meter LEDs
will momentarily display the version number of the unit’s firmware (embedded software.) Details on how to “read” the version
number is provided in the Technical Notes
section of this guide.
The Model 45DR will now begin normal
operation. The way in which the LINK/ACT,
SYS, SYNC, and PoE LEDs (all located on
the back panel below the Ethernet connector) light will depend on characteristics
related to the connected Ethernet signal
and the configuration of the unit’s Dante
interface. Details will be covered in the next
paragraph. The user is presented on the
front panel with one pushbutton switch,
two input power status LEDs, four channel
status LEDs, and four 5-segment LED level
meters. These resources are simple to operate and understand, as will be described
in later paragraphs.
Ethernet, PoE, and Dante
Status LEDs
Four status LEDs are located below the
Ethernet connector on the Model 45DR’s
back panel. The LINK/ACT LED will light
green whenever an active connection to a
100 Mb/s Ethernet network has been established. It will flash on and off in response to
data packet activity. The PoE LED will light
green whenever Power-over-Ethernet (PoE)
associated with the connected Ethernet
signal is providing operating power for the
Model 45DR. The SYS and SYNC LEDs
display the operating status of the Dante
interface and associated network. The SYS
LED will light red upon Model 45DR power
up to indicate that the Dante interface is
not ready. After a short interval it will light
green to indicate that it is ready to pass
data with another Dante device. The SYNC
LED will light red when the Model 45DR is
not synchronized with a Dante network. It
will light solid green when the Model 45DR
is synchronized with a Dante network and
an external clock source (timing reference)
is being received. It will slowly light on and
off green when the Model 45DR is part of
a Dante network and is serving as a clock
master.
How to Identify a Specific
Model 45DR
The Dante Controller software application
offers an identify command that can be
used to help locate a specific Model 45DR.
When identify is selected for a specific
unit the SYS and SYNC LEDs on that unit
will together light slowly on and off green.
This makes it a simple task to observe the
selected Model 45DR unit.
Level Meters
The Model 45DR contains four 5-segment
LED level meters. These meters are provided as a support aid during installation,
configuration, operation, and troubleshooting. The meters represent the strength of
the audio signals going to and coming
from the two party-line intercom channels.
General
The meters are organized into two groups
with each group representing one channel
of audio being sent to the party-line circuit
and one channel of audio coming from the
party-line circuit. The meters are calibrated
to reflect the level in dB relative to the
reference (nominal) level of the party-line
circuit. In the case of the Model 45DR the
nominal level of the party-line was selected
to be –10 dBu since that matches that of
typical 2-channel party-line circuits.
As an example of how the meters function
let’s review the situation where the channel 1 TO meter has its bottom three LEDs
(–18, –12, and –6) lit solid and its 0 LED
Issue 1, September 2014 Model 45DR User Guide
Page 14 Studio Technologies, Inc.
just barely lighting. This would indicate
that a signal with an approximate level of
–10 dBu is being sent to channel 1 of the
party-line intercom circuit. (Also note that
this –10 dBu signal on the party-line intercom circuit will translate to a –20 dBFS
digital audio signal on the Dante interface.
This is due to Studio Technologies selecting –20 dBFS as the reference (nominal)
level for Dante.)
Each level meter contains four green LEDs
and one yellow LED. The four green LEDs
indicate party-line circuit signal levels at or
below –10 dBu. The top LED is yellow and
indicates a signal that is 6 dB or greater
than the –10 dBu nominal level. An audio
signal that causes the yellow LED to light
doesn’t necessarily indicate an excessive
level condition, but it does provide a warning that at some stage reducing the signal
level may be prudent. Typical operation
with normal signal levels should find the
meters lighting near their 0 point. Signal
peaks may cause the yellow LEDs to flash.
But a yellow LED that lights fully during
normal operation will typically indicate excessive signal level and/or a configuration
problem with associated Dante-enabled
equipment.
Non-Optimal Signal Levels
If the meters consistently display levels
that are lower or higher than the 0 (reference) point it’s possible that a configuration issue exists. This would typically
be related to incorrect settings on the
equipment connected to the associated
Dante input and output channels. (This
situation is almost impossible to occur if
two Model 45DR units were configured
“point-to-point” as no Dante digital audio
level adjustment is provided.) With a digital matrix intercom system this problem
could be due to an incorrect configuration
having been made to a specific channel or
port. For example, the RTS ADAM system
has a published nominal level of +8 dBu,
but it’s not clear how this translates into a
digital audio level on an associated Dante
channel. Using its configuration software
it’s most likely possible to set the nominal
level of intercom key panels or ports to
something different than +8 dBu. The best
solution in this case would be to adjust the
associated OMNEO (Dante-compatible)
port such that it results in a nominal level of
–20 dBFS on the associated Dante channels. This should lead to the best performance of the Model 45DR and associated
party-line user devices.
Audio Levels and Party-Line Termination
The FROM meters display the level of signals that come from the party-line circuit.
These signals are then sent as digital audio
to the associated Dante output channels.
An issue may arise if the signals coming
from the connected party-line circuit or user
devices aren’t at a sufficient level so that a
normal meter display level can be reached.
For a party-line circuit to function correctly
the impedance (resistance to AC signals
such as audio) must be approximately 200
ohms. Typically to achieve this depends
on a single piece of equipment providing
a single audio termination. This termination, 200 ohms nominally, is almost always
made at the power supply source. But it’s
possible that another device, such as a
second active power supply on the same
party-line circuit, will cause a “double-termination” condition. This will result in a 100
ohm party-line circuit impedance and an
audio level drop of about 6 dB. Removing
the unwanted termination is the only valid
means of correcting the problem.
Model 45DR User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 15
In most cases this will be simple to solve.
It’s easily possible for the Model 45DR’s
local power source, which also provides
200 ohm termination networks for the two
channels, to be accidentally enabled when
the Model 45DR is connected to an externally-powered party-line circuit. This would
be incorrect, leading to the “double-termination” condition. Turning off the Model
45DR’s local power source by pressing
and holding the auto null button is all that
is required.
Power Status LEDs
Two green LEDs are located on the front
panel and are associated with operating
power. The PoE LED indicator will light
whenever an Ethernet connection with
Power-over-Ethernet (PoE) capability is
connected. The DC power LED will light
whenever an external DC voltage has
been applied. The acceptable range is 10
to 18 volts DC. If both power sources are
present the PoE source will provide the
Model 45DR’s operating power.
Party-Line Operating Mode
Selection
As discussed previously in this guide, the
Model 45DR provides two main operating modes. One mode is used when the
Model 45DR is required to create a partyline circuit, providing 29 volts DC and
200 ohm termination impedances. In this
mode user devices such as beltpacks can
be directly supported. When this mode
is selected the local power status LED
will be lit. The second mode allows the
Model 45DR to be connected to an existing powered party-line intercom circuit. In
this mode the local power status LED will
not be lit. To select the desired operating
mode is simple, only requiring the audio
null pushbutton switch to be pressed
and held for two seconds. The mode
will change and the local power LED will
display accordingly. The button can then
be released. The selected operating mode
will be stored in non-volatile memory so
that it will restore after a power-down/
power-up cycle.
Local Power Mode Operation
When the local power LED is lit the Model
45DR provides party-line power and 200
ohm termination impedances to create
a 2-channel party-line circuit. The partyline interface supplies 29 volts DC on pin
2 of the 3-pin XLR connectors. A maximum current draw of 240 mA is available.
This current is sufficient to power various
intercom user devices such as small user
stations and beltpacks. A common broadcast application may use RTS BP325 beltpacks. Select the connected devices so
that their total maximum current doesn’t
exceed 240 mA. That’s not always the easiest figure to calculate but a web search
will generally find specifications for all
commonly used devices. For example, a
search finds that the original version of the
BP325 consumes a maximum of 85 mA
of current. According to this figure one or
two of these units can be connected to a
Model 45DR. Newer versions of the BP325
use surface-mount component technology
and have a lower maximum current draw
of 65 mA. Up to three of these “modern”
BP325 units can easily be supported.
The active LED will light when a minimal
amount of current is flowing from the
Model 45DR to the connected user device
or devices. This current, approximately 5
mA, provides a “circuit-active” signal to
Issue 1, September 2014 Model 45DR User Guide
Page 16 Studio Technologies, Inc.
the Model 45DR’s software, indicating that
normal operation is taking place. This helps
to prevent unwanted audio signals from
passing to and from the Dante audio channels when no party-line devices are connected.
The Model 45DR’s party-line intercom
power supply circuit operates under software control. This allows detection of fault
conditions and protection of the Model
45DR’s circuitry. Upon initial Model 45DR
party-line intercom power up no monitoring
of the intercom power output takes place
for a few seconds. This allows the Model
45DR’s circuitry and the connected intercom user devices to stabilize. The active
LED, which monitors the DC voltage on pin
2 of the 3-pin XLR connectors, will light to
indicate that the output is active. After this
initial delay period monitoring becomes
active. A fault condition is detected if the
voltage on pin 2 falls below 24 for a continuous 1-second interval. The hardware
and software responds to this condition by
turning off the power source to pin 2 and
flashing the active LED as a warning. After
a 5-second “cool-down” interval the output returns to the same condition as upon
initial power up. Power is again applied to
pin 2, the active LED will light, and monitoring won’t begin for another five seconds.
A full short-circuit condition applied to the
Model 45DR’s party-line circuit will result in
a continuous cycle of six seconds on (five
seconds for start up and one second for
detection) and five seconds off.
External Party-Line Circuit
Operation
When the local power LED is not lit the
Model 45DR’s party-line interface is intended to be connected to an external party-line
circuit. The external circuit must provide
power and termination impedances to “create” the party-line, with the Model 45DR
simply serving as a user device. When
connected to an external party-line circuit
the active LED will light when the voltage
on pin 2 is equal to or greater than approximately 18. If this condition is present then
normal Model 45DR operation will be able
to take place.
Auto Null
The Model 45DR contains circuitry to automatically null the hybrid networks associated with the two party-line interface
channels. This procedure minimizes the
mixing of the audio signals being received
by and sent to the party-line circuit. Normally the nulling process is performed at
the time of initial Model 45DR configuration
but there’s no reason why it can’t be initiated any time one desires. The only time
that auto null must be performed is if conditions have changed with the party-line user
devices and wiring connected to a Model
45DR’s party-line connectors. Even a small
change to a party-line intercom circuit,
such as adding or removing a section of
cable, is often enough to require that the
auto null process be performed.
A pushbutton switch is provided to activate
the auto null process. To initiate auto
null first requires that the active LED be
lit. When the operating mode is set for
local power the active LED will light when
current is flowing from the internal power
supply. When the local power LED is not lit
the active LED must be lit, indicating that
sufficient DC voltage is present on pin 2 of
the connected party-line circuit. Once the
active LED is lit initiating the auto null function only requires pressing and releasing
Model 45DR User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 17
(“tapping”) the auto null button. The auto
null process takes place on both channels at the same time. Two LEDs provide a
visual indication of the auto null process,
flashing when the auto null process for
its respective channel is active. If the auto
null button is pressed when the active
LED is not lit the auto null process will
not start. The auto null LEDs will quickly
flash on and off a few times to indicate this
condition.
An auto null sequence begins with the
muting of the audio input and output signal paths associated with the Dante input
and output channels. This is followed by
a short period of 24 kHz signal that is sent
to both channels of the party-line intercom
interface. This will turn off microphones
on those connected user devices that are
compatible with the RTS TW-Series “mic
kill” protocol. The actual auto nulling process is performed next. A series of tones
will be sent to each of the party-line interface channels. Other Model 45DR circuitry,
under software control, will rapidly perform
adjustments to achieve the best null possible. After the adjustments have been
made the results are stored in non-volatile
memory. Once the process is complete
the Dante audio input and output paths
are again activated.
If possible, prior to performing an auto
null it’s polite to warn all personnel who
are actively using the connected partyline intercom devices. The tones sent to
the party-line circuit during the nulling
process are not excessively loud or obnoxious, but most users might want to
remove their headsets during the process.
In addition to warning users, it might be a
good time to ask them to mute any active
microphones. While the automatic “mic
kill” signal will apply to many user devices it
may not apply to all. Muting microphones
is significant as obtaining a “deep” null
requires that no extraneous signals be
present on the intercom circuit.
USB Interface
A USB type A connector and associated
status LED is located on the back panel
of the Model 45DR. This data interface is
used only for updating the unit’s firmware
(embedded software). No audio data of any
kind will pass through it. For details please
refer to the Technical Notes section of this
guide.
Technical Notes
3-Position Header
An internal 3-position header connector
allows support for an alternate cover. The
cover, purchased as an option, has an
Anton-Bauer QR-Gold battery bracket that
is electrically wired in parallel with the 4-pin
XLR DC input connector. The header, located on the Model 45DR’s printed circuit
board, is Molex® part number 22-23-2031.
It mates with Molex housing number 22-01-
3037. To make the interconnection, separate crimp terminals are attached to three
loose wires and then “snapped” into the
housing. Molex part number 08-50-0114
specifies crimp terminals that are appropriate for 22 to 30 gauge wires. These terminals are available worldwide from sources
such as Digi-Key (www.digikey.com).
Software Version Display
As part of the Model 45DR’s power-up
sequence the unit’s software version
number is displayed. This is useful when
Issue 1, September 2014 Model 45DR User Guide
Page 18 Studio Technologies, Inc.
working with factory personnel on application support and troubleshooting situations. The five TO channel 2 LEDs are
used to display the major release number
with a range of 1 through 5. The five LEDs
associated with FROM channel 2 are used
to display the release sub-number which
ranges from 1 through 5. Refer to Figure
3 for a detailed view of the LEDs and the
corresponding software version numbering scheme. The Model 45DR’s initial
software release is version 1.1 which is
represented by the bottom LED of each
column being lit.
Major Release Number Release Sub-Number
O 4 .4 O
O 3 .3 O
O 2 .2 O
1 .1
Figure 3. Detail of front panel showing the
status LEDs that display the software version.
In this example, the software version is 1.1.
MCU Firmware Update
Procedure
It’s possible that updated versions of the
firmware (embedded software) that runs
the Model 45DR’s microcontroller (MCU)
integrated circuit will be released to add
features or correct issues. (Contact Studio
Technologies’ technical support to review
the available firmware.) The unit has the
ability to automatically load revised files
into the MCU’s non-volatile memory by way
of its USB interface. The Model 45DR implements a USB host function that directly
supports connection of a USB flash drive.
The Model 45DR’s MCU updates using a
file named M45DR.bin.
The update process begins by preparing
a USB flash drive. The flash drive doesn’t
have to be empty (blank) but must be in the
personal-computer-standard FAT32 format.
Save the new firmware file in the root directory with a name of M45DR.bin. Studio
Technologies will supply the MCU file inside
a .zip archive file. While the firmware file
inside of the zip file will adhere to the naming convention required by the Model 45DR,
the name of the zip file itself will include the
MCU file’s version number. For example,
a file named M45DRv1r1MCU.zip would
indicate that version 1.1 of the firmware
(M45DR.bin) is contained within this zip
file. Two of the LED meters should be used
to confirm that the correct firmware version
has been successfully installed.
Model 45DR User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 19
To install the firmware file follow these
steps:
1. Remove power from the Model 45DR.
This will entail removing the Ethernet
connection if it is providing PoE power
and/or removing the external source of
12 volts DC if that is being used.
2. Ensure that nothing is present in the
USB port. Then again apply power to
the unit and “read” the currently loaded
firmware version during the power-up
sequence using the channel 2 level
meters. (Refer to the Software Version
Display paragraph earlier in this section.) Note this for later reference.
3. Remove power from the Model 45DR.
4. Insert the prepared USB flash drive into
the Model 45DR’s USB port, located on
the back panel of the unit.
5. Apply power to the Model 45DR. Power
can be provided by Power-over-Ethernet (PoE) associated with a connected
Ethernet signal or can be from an external 12 volt DC source.
6. The Model 45DR will run a “boot
loader” program that will immediately
load the new MCU (M45DR.bin) file.
This process takes only a few seconds.
During this time period the LED located
below the USB connector will flash
slowly on and off green. Once the entire
loading process is over, taking approximately 10 seconds, the Model 45DR will
restart using the newly-loaded firmware.
8. Apply power to the Model 45DR and
“read” the MCU’s firmware version
number by observing the channel 2
level meters. Ensure that this is the desired version and that it’s different from
that noted in step 2.
Note that upon power being applied to the
Model 45DR if the USB flash drive doesn’t
have the correct file (M45DR.bin) in the
root folder no harm will occur. Upon power
up the USB LED will flash on and off
rapidly for a few seconds to indicate this
condition and then normal operation using
the unit’s existing firmware will begin.
Ultimo Firmware Update
As previously discussed in this guide, the
Model 45DR implements Dante connectivity using the Ultimo integrated circuit from
Audinate. This 2-input/2-output device can
be updated by way of the Model 45DR’s
Ethernet connection. As of the date of writing this guide it’s not evident as to whether
or not newer firmware will ever need to be
loaded. If so, it will be provided by Studio
Technologies.
7. At this time the Model 45DR is functioning with the newly-loaded firmware and
the USB flash drive can be removed.
But to be conservative, remove power
first and then remove the USB flash
drive.
Issue 1, September 2014 Model 45DR User Guide
Page 20 Studio Technologies, Inc.
Specifications
Power Sources:
Power-over-Ethernet (PoE): class 3 (medium
power) per IEEE 802.3af
External: 10 to 18 volts DC, 1.0 amp max @
12 volts DC
Network Audio Technology:
Type: Dante Audio-over-Ethernet
Bit Depth: up to 24
Sample Rate: 48 kHz
Number of Output (Transmitter) Channels: 2
Number of Input (Receiver) Channels: 2
Network Interface:
Type: twisted-pair Ethernet, Power-over-Ethernet
(PoE) supported
Data Rate: 100 Mb/s (10 Mb/s Ethernet not
supported)
General Audio:
Frequency Response (PL to Dante): –0.3 dB @
100 Hz (–4.8 dB @ 20 Hz), –2 dB @ 8 kHz (–2.6 dB
@ 10 kHz)
Frequency Response (Dante to PL): –3.3 dB @
100 Hz (–19 dB @ 20 Hz), –3.9 dB @ 8 kHz
(–5.8 dB @ 10 kHz)
Distortion (THD+N): <0.15%, measured at 1 kHz,
Dante input to PL interface pin 2 (0.01% pin 3)
Signal-to-Noise Ratio: >65 dB, A-weighted,
measured at 1 kHz, Dante input to PL interface
pin 2 (73 dB, PL interface pin 3)
Party-Line (PL) Intercom Interface:
Type: 2-channel analog PL, unbalanced (pin 1
common; pin 2 DC with channel 1 audio; pin 3
channel 2 audio)
Compatibility: 2-channel PL intercom systems
such as those offered by RTS®
Power Source: 29 volts DC, 240 mA maximum
Impedance – Local PL Power Not Enabled:
>10 k ohms
Impedance – Local PL Power Enabled: 200 ohms
Analog Audio Level: –10 dBu, nominal, +3 dBu
maximum, PL interface pin 2 (+7 dBu, PL interface
pin 3)
“Call Light” Signal: 20 kHz, ±1%, square wave
“Mic Kill” Signal: 24 kHz, ±1%, square wave
Party-Line (PL) Hybrids:
Topology:
for resistive, inductive, and capacitive loads
Nulling Method: automatic upon user initiation,
processor implements digital control of analog
circuitry; settings stored in non-volatile memory
Nulling Line Impedance Range: 120 to 350 ohms
Nulling Cable Length Range: 0 to 3500 feet
Trans-Hybrid Loss: >50 dB, typical at 800 Hz,
PL interface pin 2 (>55 dB, PL interface pin 3)
Meters: 4
Function: displays level of audio input and output
channels
Type: 5-segment LED, modified VU ballistics
Connectors:
Party-Line (PL) Intercom: 3-pin male and female
XLR
Ethernet: Neutrik etherCON RJ45
External DC:
USB: type A receptacle
Dimensions – Overall:
8.7 inches wide (22.1 cm)
1.72 inches high (4.4 cm)
8.3 inches deep (21.1 cm)
Mounting Options: single- or dual-unit rack-mount
front panels; uses one space (1U) in a standard
19-inch rack
Weight: 1.7 pounds (0.77 kg); rack-mount front
panels add 0.2 pounds (0.09 kg)
3-section analog circuitry compensates
4-pin male XLR
2
Specifications and information contained in this
User Guide subject to change without notice.
Model 45DR User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 21
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