A Feature-Packed Interruptible Foldback (IFB) System
A Highly Integrated, 2-Channel IFB
System for Mobile Applications
The IFB Plus Series is designed for electronic newsgathering (ENG) trucks, satellite news-gathering (SNG)
trucks, and small production vehicles. Interruptible foldback (also known as talent cueing) allows reporters and
other on-air talent to receive program audio along with
audio cues from production personnel, generally directors and producers. The design and implementation of
a studio IFB system can be quite complex, yet normally
remains the same from day to day. Talent and production
personnel, along with the IFB equipment, are physically
located in the same facility.
Overview
Mobile IFB applications can present increased challenges
as the number and variety of program sources, interrupt
sources, and configuration possibilities quickly multiply.
Program audio can come from many sources, including
off-air receivers, two-way radios, telephone lines, satel
lite receivers, and cellular telephones. Interrupt audio
(talent cues) may be received with the program material
connected via telephone lines or may need to come from
the mobile unit itself. The ability to provide IFB audio to
a number of destinations is also required. These include
talent “beltpack” amplifiers, transmitters used with wire
less receivers, and intercom systems.
A mobile IFB system must be easy to set up and quick
to configure. It must be able to withstand the day in,
day out punishment of life “on the road.” Meeting these
System Components
•
Model 2A Central Controller
•
Model 22 Access Station
•
Model 24 Access Station
•
Model 32A Talent Amplifier
•
Model 33A Talent Amplifier
•
Optional accessories include:
- Model 11A Gooseneck Microphone
-
Model 25A and 27A Rack Adapter
-
Model 27A Rack Adapter
- Model 28A Panel Adapter
diverse requirements is made more difficult by the space
restrictions imposed by mobile facilities. Studio Technolo
gies has addressed these requirements with the IFB Plus
Series products. The IFB Plus Series consists of the
Model 2A Central Controller, the Model 22 and Model 24
Access Stations, the Model 32A and Model 33A Talent
Amplifiers, and supporting accessories. These products
combine the best features of studio IFB systems along
with the special requirements of mobile applications. The
end result is an IFB system that is flexible, versatile, and
extremely space efficient.
The heart of the IFB Plus Series is the Model 2A Central
Controller. This single-rack-space unit (1U) offers a wide
range of features all optimized for mobile applications.
These include multiple program inputs, telephone in
terfaces, voice-operated (VOX) interrupt, level meters,
Model 2A Central Controller Front Panel
Model 2A Central Controller Back Panel
IFB Plus Series, Issue 6, Page 1
monitor amplifier output, and an internal interrupt microphone. In addition, up to four Model 22 or Model 24 Access
Stations can be connected to a Model 2A, allowing producer
or director positions to access the IFB channels.
The Model 2A allows connection of up to six Model 32A
or Model 33A Talent Amplifiers. These portable “belt
pack” units interconnect with a Model 2A using standard
microphone cables. Both DC power and two channels of
audio are supplied on just one 3-conductor cable, provid
ing personnel with convenient, reliable access to the two
IFB channels.
Model 2A Central Controller
Mounted in a single space (1U) of a 19-inch rack, the
Model 2A provides everything required to implement a
2-channel IFB system. Features include multiple program
inputs, telephone interfaces, voice-operated (VOX) inter
rupt, level meters, monitor amplifier output, and an internal
interrupt microphone. In addition, up to four Model 22 or
Model 24 Access Stations can be connected to a Model
2A, allowing producer or director positions to access the
IFB channels. In addition, up to six Model 32A or Model
33A Talent Amplifiers can be connected to a Model 2A.
These portable “beltpack” units interconnect with a Model
2A using standard microphone cables. Both DC power and
two channels of audio are supplied on just one 3-conductor
cable, providing personnel with convenient, reliable access
to the two IFB channels.
The Model 2A packs numerous features into a rugged yet
lightweight 1U enclosure. Standard connectors are used
throughout, including 3-pin XLR, ¼-inch 2-conductor,
9-position D-subminiature, and modular telephone (RJ11)
jacks. A source of 100-240 volts, 50/60 hertz is connected
via a detachable mains cord and provides power for the
Model 2A.
IFB Channels
The Model 2A contains two independent IFB channels. Each
channel has individual controls and indicators, including
program source select switches, program level control,
5-segment LED level meter, and LED status indicators. The
features of one of two identical channels will be highlighted
in this paragraph. Six switches allow the four program
audio inputs and audio coming from the two telephone in
terfaces to be selected as program audio sources. A rotary
level control allows adjustment of the program audio level
relative to that of the non-adjustable interrupt audio level.
A 5-segment LED meter displays the level of the composite
IFB audio signal. (The composite audio signal is the com
bination of the selected program audio source(s) and the
interrupt audio source(s).) The level meter facilitates the
rapid setting of the program level control, as well as provid
ing a general indication of the IFB channel’s signal level.
Each channel’s composite IFB audio signal (a mix of program and interrupt audio) is sent to four places: a line-level
output, the talent amplifier output, telephone interface 2,
and the monitor output section. Each line output provides
an electronically balanced, line-level signal that interfaces
with external equipment via a 3-pin XLR connector. The
talent amplifier output provides IFB channel 1 and 2 audio,
along with 24 volts DC power on one 3-pin XLR connector. Any combination of up to six Model 32A or Model 33A
units can be connected to the talent amplifier output. For
application flexibility, the talent amplifier output provides
200 ohm line impedances on both of its output channels.
This allows direct connection of not just listen-only devices,
such as the Models 32A and 33A, but party-line (PL) user
beltpacks as well. In this way popular PL beltpacks, from
suppliers such RTS® and Clear-Com®, can be connected
and used to create a small PL intercom system that includes
IFB listen. A selector switch associated with telephone
interface 2 can be used by an operator to send either IFB
channel 1 or 2 out the connected phone line. The monitor
output section allows loudspeaker monitoring of audio from
either IFB channel 1 or 2. (An optional external loudspeaker
is required.)
Program Inputs
The Model 2A contains four line-level program inputs. Each
can be individually assigned to the two IFB channels, with
the ability to assign multiple program inputs to an IFB
channel. Program signals enter the unit via four 3-pin XLR
connectors located on the unit’s back panel. The program
inputs are electronically balanced and feature low noise,
low distortion, and high common mode signal rejection.
Each program input has a trim potentiometer associated
with it. The trim pots, accessible from the back panel, allow
source signals with a nominal level of –10 to +8 dBu to be
correctly utilized.
Program audio is muted whenever interrupt activity is
taking place. Solid-state circuitry is used to provide noisefree audio switching with essentially no “clicks” or “pops”
added. If desired, a program “dim” rather than a full mute
can be implemented by adding two resistors to the Model
2A’s circuit board.
Compressor Circuits
The two IFB channels contain studio-quality compressor
circuitry to control the dynamic range of the interrupt
audio. These play an important role in how the Model 2A
maintains high audio quality, specifically evening out level
variations presented by the talk signals associated with
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Studio Technologies, Inc. IFB Plus Series, Issue 6, Page 2
various IFB users. The compressors make talent cues more
intelligible and prevent abnormally high signal levels from
reaching user’s ears. The resulting audio quality is very,
very good.
Telephone Interfaces
The Model 2A contains two telephone interfaces. Both
interfaces can be used to bring audio into the Model 2A
from the outside world. These two audio signals can be
independently assigned as program sources for IFB chan
nels 1 and 2, as well as being used as an audio source for the
voice operated (VOX) interrupt function. Each telephone
interface has a receive-level trim potentiometer that is ac
cessible via a small hole in the front panel. The large level
variations that can be presented by a telephone line can
make “on the fly” level trimming a useful feature. In addi
tion to receiving audio, telephone interface 2 can be used
to originate an IFB “feed” (IFB output). A switch selects
if audio will be received from the outside world, or if audio
from IFB channel 1 or 2 will be sent out the interface.
The telephone interfaces contain a unique feature which
allows two very different types of telephone “lines” to be
correctly interfaced. Each interface can be independently
set to operate in either a telephone line mode or a standard
audio mode. A telephone line has the profile of being a
2-wire, DC-biased (normally –48 volts) circuit provided
by a local telephone company, long-distance carrier, or
private telephone system. A standard audio signal could be
provided by, for example, a “dry” (no DC voltage provided)
fax adapter associated with a cellular telephone.
When an interface is set to the telephone line mode and a
telephone line with DC voltage is connected, full monitor
ing and control is implemented. Each interface contains a
switch that allows the telephone line to be answered (taken
“off hook”) or hung up (placed “on hook”). DC loop cur
rent is monitored when the interface is active (off hook).
If a telco-provided disconnect signal (a momentary break
in loop current) is detected the interface will automatically
return to its idle (on-hook) state. Telephone interface 1
contains an LED status indicator that lights whenever loop
current is detected. Telephone interface 2 has a status LED
that “flashes” when a ringing signal is detected and lights
continuously when loop current is detected. Interface 2 also
implements an auto answer function which can automati
cally take the telephone line to the answer (off-hook) state
when a ringing signal is detected.
In many cases a “telephone line” in a mobile broadcast ap
plication is actually provided by a cellular telephone. This
cellular telephone may provide a “dry” (no DC loop current)
audio output signal. The standard audio mode was designed
expressly to interface with this “cell phone” arrangement.
In this mode, the interface’s loop current-specific features
are disabled, and the interface appears electrically as a
transformer-coupled balanced audio interface.
When an interface has been set for the standard audio
mode its front-panel line status switch is inactive as is its
loop status LED. Also inactive in the standard audio mode
is telephone interface 2’s auto answer function. An LED
associated with each telephone interface displays when
the standard audio mode is selected.
Voice Operated (VOX) Interrupt
The Model 2A contains circuitry to allow an audio signal to
serve as both an interrupt audio source and a control signal.
This eliminates the need for a separate push-to-talk button
or contact closure. The VOX feature allows an audio signal
from a remote source, such as a 2-way radio or telephone
line, to serve as the interrupt source. The VOX function was
optimized for detecting audio signals in the voice band. As
voice detection is not a trivial task, great care was taken
when designing the circuitry to support this function.
Three signals can serve as the audio source for the VOX
interrupt function: receive audio from telephone interface
1, receive audio from telephone interface 2, or the auxiliary
audio input. The auxiliary audio input is a separate line-level
audio input that is only associated with the VOX interrupt
function. A 3-position switch selects which source will be
used. A second 3-position switch is used to select which
IFB channel is to respond to the VOX interrupt function.
The VOX interrupt function can be assigned to only one
IFB channel at a time or it can be disabled. Each IFB chan
nel contains an LED indicator light to display when a VOX
(voice-activated) interrupt is taking place.
Internal Interrupt Microphone
Contained behind the Model 2A’s front panel is an internal
interrupt microphone. Associated with the microphone are
two switches, allowing the internal microphone to interrupt
IFB channel 1, channel 2, or both channels 1 and 2.
Monitor Output
The Model 2A contains a simple but excellent monitor
output section. At the core is a 4 watt high-performance
audio amplifier designed to drive an 8 ohm (or greater)
loudspeaker. (The speaker is optional and is provided as
part of an installation.) Associated with the monitor output
are a 3-position source select switch and a level control.
The switch selects whether IFB channel 1 or IFB channel
2 will be monitored, as well as having an off position. A
click-free circuit mutes the monitor output whenever the
internal microphone or a Model 22 or Model 24 Access
Station is interrupting either IFB channel.
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Studio Technologies, Inc. IFB Plus Series, Issue 6, Page 3
Model 22 Access Station
The Model 22 Access Station and related accessories (all
purchased separately) provides the capability for adding
up to four additional interrupt locations. Model 22 units
are intended to be installed at positions convenient to
producers, directors, or other personnel who need to “cue”
talent and related personnel. The unit consists of a metal
chassis containing two lighted pushbutton switches, unbal
anced microphone and balanced line inputs, and status and
control circuitry.
The two high-quality backlit pushbutton switches provide
access to the Model 2A’s two IFB channels. The lights in
the switches display when an interrupt is taking place on
its respective channel; lighting brightly when IFB is active
and dim when IFB is idle. An input select switch allows con
nection of a Model 11A Gooseneck Microphone or external
line-level signal source. The electronically balanced linelevel input allows interfacing with other communications
equipment, such as “hot mic” signals from an intercom
user station.
The Model 22 can be configured to mute the Model 2A’s
monitor amplifier output. This function will prevent acoustic
feedback from occurring when a Model 22 is located close
to the Model 2A’s monitor speaker.
Model 22 Access Stations are linked to the associated
Model 2A Central Controller via 9-pin D-subminiature
female connectors. Each access station contains two
connectors, allowing a simple daisy-chain installation.
The nine leads carry all signals; audio, control, status
lamp (tally), and power. The Model 2A provides all power
required by the access stations. The Model 25A 19-Inch
Rack Adapter is available to mount a Model 22 and a Model
11A Gooseneck Microphone in one space (1U) of a stan
dard 19-inch rack. The Model 28A Panel Adapter allows a
Model 22 and a Model 11A Gooseneck Microphone to be
mounted in a panel opening.
Model 24 Access Station
The Model 24 is similar to the Model 22 with the exception
that it works with two Model 2A units. In this way produc
tion personnel can access all four of the IFB channels
associated with the two Model 2A units. Up to four Model
24s can be connected to each Model 2A. A Model 24 unit
consists of a metal chassis that holds five lighted pushbut
ton switches, audio and control circuitry, and microphone
and line input connectors.
Each of the four IFB channel pushbutton switches display
when an interrupt is taking place on its respective chan
nel. A fifth button is specified as “all call” and lights when
pressed. The Model 24 supports connection of an optional
Model 11A Gooseneck Microphone or a line-level signal.
The latter is transformer-balanced, allowing compatibility
with virtually any line-level source. A switch is used to
select the interrupt audio source. A second switch allows
the Model 24 to mute the monitor output on each of the
Model 2A units whenever an IFB channel is activated.
Model 24 Access Stations connect to the associated Model
2A units using two 9-pin D-subminiature connectors. The
nine conductors that link each Model 2A with the Model 24
support all the audio, signaling, and power requirements.
No external power source is required. The optional Model
27A allows a Model 24, along with a Model 11A Gooseneck
Microphone, to be mounted in one space (1U) of a standard
19-inch rack enclosure.
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-
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Model 22 Access Station
(shown mounted in optional Model 25A Rack Adapter
with optional Model 11A Gooseneck Microphone)
Model 24 Access Station
(shown mounted in optional Model 27A Rack Adapter
with optional Model 11A Gooseneck Microphone)
Studio Technologies, Inc. IFB Plus Series, Issue 6, Page 4
Model 32A and Model 33A Talent
Amplifiers
Model 32A and Model 33A Talent Amplifiers, purchased
separately, are self-contained “beltpack” units that drive
talent earpieces or headsets. An audio cable with 3-pin
XLR connectors on its ends links the talent amplifiers with
a Model 2A. Each Model 32A and Model 33A contains both
a male and female 3-pin XLR connector, allowing simple
“loop through” connection of multiple units. Up to six of the
talent amplifiers can be connected to, and powered by, a
single Model 2A Central Controller. On each talent ampli
fier the audio output signal is provided on both a ¼-inch
2-conductor phone jack and a 3.5 mm output jack. An LED
on each unit lights whenever power is present, providing
setup assistance and user confidence. Identical in size, each
is housed in a lightweight, yet rugged, aluminum housing.
A belt clip allows it to be attached to belts, clipboards, scab
bards, pizza boxes, production assistants, etc. An optional
mounting adapter kit is available, allowing a Model 32A or
Model 33A to be installed in a permanent location.
The Model 32A is typically used by on-air personnel, and
contains a source selection switch, along with an output
Model 32A (top) and
Model 33A (bottom) Talent Amplifiers
level control. Either IFB channel 1 or IFB channel 2 can be
sent to the talent, along with the desired audio “volume.”
The Model 33A is unique in that a “mix” of IFB channels 1
and 2 can be created. Two level controls, along with a source
selection switch, allows camera and production personnel
to hear IFB cues from either or both channels. This allows
IFB signals intended for both production personnel and
on-air talent to be simultaneously monitored.
IFB Plus Specifications
Model 2A Central Controller
General Audio Parameters (Program Input to Main
Output):
Overall Frequency Response: 20 Hz to 20 kHz, –0.3 dB @ 20 Hz,
–0.8 dB @ 20 kHz
Distortion (THD+N): 0.008%
S/N Ratio: 89 dB, ref. +4 dBu nominal
Interrupt Audio Compressor/Limiters: one per IFB channel,
studio quality, dual slope, threshold 1 dB above nominal
Connectors:
Access Station: DE-9F (9-pin D-subminiature, female)
Program and Aux Audio Inputs: 3-pin female XLR
Line Outputs: 3-pin male XLR
Talent Amplifier Output: 3-pin male XLR
Telephone Interfaces: 2, RJ11 modular jack (6-position modular
with pins 3 and 4 implemented)
Monitor Amplifier Output: ¼-inch, 2-conductor phone jack
AC Mains Input: 3-blade, IEC 320 C14-compatible (mates
with IEC 320 C13)
Internal Interrupt Microphone: electret condenser
Program Inputs:
Type: electronically balanced, direct coupled
Impedance: 24 k ohms
Level: +4 dBu, nominal, trim adjustable over a range of –10 to
+8 dBu
Auxiliary Audio Input:
Type: electronically balanced, direct coupled
Impedance: 24 k ohms
Level: +4 dBu, nominal, trim adjustable over a range of –10 to
+8 dBu
Application: used with voice operated (VOX) interrupt function
4
Line Outputs: 2, 1 per IFB channel
Type: electronically balanced, capacitor coupled, intended to
drive 2000 ohm or greater loads
Level: +4 dBu, nominal, +25 dBu maximum
Talent Amplifier Output:
Applications: provides power and audio signals for up to six
Model 32A or Model 33A Talent Amplifiers; also allows connection
of party-line (PL) intercom beltpacks
Connections: common on pin 1, DC (+24 volts DC nominal)
modulated with channel 1 audio (–10 dBu nominal) on pin 2,
and channel 2 audio (–10 dBu nominal) on pin 3
Output Impedance: 200 ohms nominal from pin 2 to 1; 200 ohms
nominal from pin 3 to pin 1; RTS® and Clear-Com® compatible
Maximum DC output current: 250 milliamperes
Maximum Audio Output Level: +10 dBu
Voice Operated (VOX) Interrupt Function:
Input Source: audio from telephone interface 1, audio from
telephone interface 2; or auxiliary audio input, selectable
Output: IFB channel 1 or 2, selectable
Detection Bandpass: 400 to 1400 Hz, nominal
Detect Time: <1 mSec
Release Time: 320 mSec, nominal
Telephone Interfaces 1 and 2:
Operating Modes: switch selectable for use with telephone lines
or standard balanced or unbalanced audio signals
Receive Audio Level: –15 dBu, nominal, trim adjustable ±8 dB
Telephone Line Requirements: 2-wire, loop start, 10 milliamperes
loop current minimum
Telephone Line Disconnect: manual, using front-panel switch;
automatic, after detection of 250 mSec, nominal, break in loop
current
Telephone Line Interface Control: switch on front panel allows
manual answer (“off-hook”) and manual hang-up (“on-hook”)
functions
Studio Technologies, Inc. IFB Plus Series, Issue 6, Page 5
Telephone Interface 2—Additional Features:
Auto Answer (when set for telephone line operation): configurable
for 1, 2 or 4 rings or disabled
Audio Routing Control: switch on front panel allows Interface 2
to receive audio, or send IFB channel 1 or 2 audio
Send Audio Level: –6 dBu, nominal
Monitor Output:
Power: 4 watts RMS into 8 ohms @ 1% THD+Noise
Application: designed to drive loads of 8 ohms or greater
Access Station Interface: allows connection of up to four
Model 22 or Model 24 Access Stations
AC Mains Input:
24 watts maximum
Dimensions (Overall):
19.0 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
9.2 inches deep (23.4 cm)
Mounting: one space (1U) in a standard 19-inch rack
Weight:
4.5 pounds (2.1 kg)
100-240 volts (–15/+10%), 50/60 Hz,
Model 22 Access Station
Application: provides remote 2-channel interrupt (talk) location
based on a Model 2A Central Controller unit; up to four Model 22
units can be connected to a Model 2A Central Controller
Power Requirements: 18 volts DC, 25 milliamperes maximum,
provided by connected Model 2A Central Controller
Interconnection:
Two DE-9F (9-pin D-subminiature female) connectors. One con
nector intended to link Model 22 to Model 2A Central Controller.
The second connector, wired in parallel with the first, is designed
to allow “loop through” installation for connection to additional
Model 22(s).
Pushbutton Switches: 2
Type: backlit, momentary, EAO 99-series
Lamp Type: incandescent, T-1, bi-pin, 18 V, 26 milliamperes,
0.5 watt equivalent to EAO Switch Corp. 11-903-2, Wamco
0L1100BPE, Lamptronics AS25-8
Audio Inputs: electret microphone or line level, switch selectable
Microphone Input:
Compatibility: 2-wire electret, designed for use with Studio
Technologies’ Model 11A Gooseneck Microphone (purchased
separately)
Intended Input Level: –25 dBu nominal
Microphone Power: +5 volts DC, current limited; applied to
microphone “high” lead
Connector: three terminals on a screw terminal strip
Line Input:
Type: electronically balanced, capacitor coupled, compatible with
balanced or unbalanced audio signals
Input Impedance: 24 k ohms
Common Mode Rejection: 100 dB at DC and 60 Hz, 70 dB at
20 kHz, 62 dB at 40 kHz (typical)
Input Level: –15 to +10 dBu, input level adjustable via trim
potentiometer
Connector: two terminals on a screw terminal strip
Dimensions (Overall):
6.4 inches wide (16.3 cm)
1.6 inches high (4.1 cm)
5.2 inches deep (13.2 cm)
Mounting: rack mounted using Model 25A 19-Inch Rack Adapter
(purchased separately)
Adapter (purchased separately); custom mounting easily accomplished
Weight:
0.8 pounds (0.4 kg)
, panel mounted using Model 28A Panel
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Model 24 Access Station
Application: provides remote 4-channel interrupt (talk) location
for IFB system based on two Model 2A Central Controller units,
up to four Model 24 units can be connected to the two Model 2A
Central Controllers
Power Requirements: 18 volts DC, 50 milliamperes nominal,
provided by connected Model 2A Central Controller
Interconnections: two DE-9F (9-pin D-subminiature female)
connectors; each links the Model 24 with a Model 2A Central
Controller
Interrupt Switches: 5
Functions: IFB 1-4, All Call
Type: momentary pushbutton, EAO 99-series, all backlit, tally
indication for IFB 1-4 functions
Microphone Input:
Compatibility: 2-wire electret, designed for use with Studio
Technologies’ Model 11A Gooseneck Microphone (purchased
separately)
Intended Input Level: –25 dBu nominal
Connector: three terminals on a screw terminal strip
Line Input:
Type: transformer coupled, compatible with balanced or unbal
anced audio signals
Input Impedance: 40 k ohms, nominal
Input Level: –15 to +10 dBu, adjustable using trim potentiometer
Connector: two terminals on a screw terminal strip
Monitor Muting: switch selectable, allows Model 24 interrupt
activity to mute monitor amplifier outputs on Model 2A Central
Controllers
Dimensions (Overall):
6.4 inches wide (16.3 cm)
1.6 inches high (4.1 cm)
5.2 inches deep (13.2 cm)
Mounting: rack mounted using Model 27A 19-Inch Rack Adapter
(purchased separately); can also be flush mounted in customfabricated rectangular opening in enclosure or work surface
Weight:
0.8 pounds (0.35 kg)
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Model 25A 19-Inch Rack Adapter
Application: intended for use with Model 22 Access Station and
Model 11A Gooseneck Microphone
Dimensions (with Model 22 attached):
19.0 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
5.2 inches deep (13.2 cm)
Mounting: one space (1U) in a standard 19-inch rack
Weight (with Model 22 attached):
1.6 pounds (0.7 kg)
Model 27A 19-Inch Rack Adapter
Application: intended for use with one Model 24 Access Station
and one Model 11A Gooseneck Microphone
Dimensions (with Model 24 attached):
19.0 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
5.2 inches deep (13.2 cm)
Mounting: one space (1U) in a standard 19-inch rack
Weight (with Model 24 attached):
1.6 pounds (0.7 kg)
Studio Technologies, Inc. IFB Plus Series, Issue 6, Page 6
Model 28A Panel Adapter
Application: intended for use with one Model 22 Access Station
and one Model 11A Gooseneck Microphone
Dimensions (with Model 22 attached):
8.0 inches wide (20.3 cm)
2.75 inches high (7.0 cm)
5.2 inches deep (13.2 cm)
Mounting: designed to be mounted in a panel opening; recommended opening size 6.5 inches wide (16.5 cm), 1.7 inches high
(4.3 cm), 6.5 inches minimum depth (16.5 cm)
Weight (with Model 22 attached):
1.3 pounds (0.6 kg)
Model 32A Talent Amplifier
Applications: directly compatible with talent amplifier output
on Model 2A Central Controller; also compatible with standard
single- and dual-channel IFB and party-line intercom circuits
Indicator Light: red LED indicates operation of internal power
supply
Connectors:
Input: 3-pin female XLR
Loop Through: 3-pin male XLR
Output: ¼-inch and 3.5 mm 2-conductor jacks; sleeve common,
tip “hot,” ring not used
IFB/Intercom Input Wiring Scheme:
Pin 1: common for DC and audio
Pin 2: DC with channel 1 audio (dual-channel circuits) or DC only
(single-channel circuits)
Pin 3: channel 1 audio (single-channel circuits) or channel 2 audio
(dual-channel circuits)
Power Requirement: 18-35 volts DC, 15 milliameres
quiescent, 40 milliamperes maximum
Output:
Compatibility: intended for connection to mono (2-conductor)
headsets or earpieces with nominal impedance of 150 ohms
or greater
Type: voltage driver
Input/Output Gain: 28 dB, maximum
Maximum Output Voltage: 8 volts peak-to-peak, 1 kHz,
150 ohm load
Frequency Response: 40 Hz-20 kHz, ±1 dB, 150 ohm load
Distortion (THD+N): 0.03%, 1 kHz, 150 ohm load, 0 dBu out
Dimensions (Overall):
3.25 inches wide (8.3 cm)
1.8 inches high (4.6 cm)
3.95 inches deep (10.0 cm)
Mounting: intended for portable applications; contains integral
belt clip; optional mounting adapter kit allows Model 32A to be
permanently mounted
Weight: 0.6 pounds (0.3 kg)
Model 33A Talent Amplifier
Applications: directly compatible with talent amplifier output
on Model 2A Central Controller; also compatible with standard
single- and dual-channel IFB and party-line intercom circuits
Indicator Light: red LED indicates operation of internal power
supply
Connectors:
Input: 3-pin female XLR
Loop Through: 3-pin male XLR
Output: ¼-inch and 3.5 mm 2-conductor jacks; sleeve common,
tip “hot,” ring not used
IFB/Intercom Input Wiring Scheme:
Pin 1: common for DC and audio
Pin 2: DC with channel 1 audio (dual-channel circuits) or DC only
(single-channel circuits)
Pin 3: channel 1 audio (single-channel circuits) or channel 2 audio
(dual-channel circuits)
Power Requirement: 18-35 volts DC, 15 milliameres
quiescent, 40 milliamperes maximum
Output:
Compatibility: intended for connection to mono (2-conductor)
headsets or earpieces with nominal impedance of 150 ohms
or greater
Type: voltage driver
Input/Output Gain: 28 dB, maximum
Maximum Output Voltage: 8 volts peak-to-peak, 1 kHz,
150 ohm load
Frequency Response: 40 Hz-20 kHz, ±1 dB, 150 ohm load
Distortion (THD+N): 0.03%, 1 kHz, 150 ohm load, 0 dBu out
Dimensions (Overall):
3.25 inches wide (8.3 cm)
1.8 inches high (4.6 cm)
3.95 inches deep (10.0 cm)
Mounting: intended for portable applications; contains integral
belt clip; optional mounting adapter kit allows Model 33A to be
permanently mounted
Weight: 0.6 pounds (0.3 kg)
Features and specifications subject to change without notice.
Studio Technologies, Inc.
Skokie, Illinois USA
+1 847-676-9177
studio-tech.com
50136-1213, Issue 6
Studio Technologies, Inc. IFB Plus Series, Page 7
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