Datasheet

Studio Technologies, Inc. Model 45A 2-Wire to 4-Wire Interface, Issue 1, Page 2
Specifications
General Audio:
Frequency Response: ±2.5 dB, 100 Hz to 8 kHz
Distortion (THD+N): <0.2%, measured at
1 kHz, 4-wire input to 2-wire interface pin 2
Signal-to-Noise Ratio: >55 dB, measured at
1 kHz, 4-wire input to 2-wire interface pin 2
2-Wire Party-Line (PL) Intercom Interface:
Type: 2-channel party-line, unbalanced (pin 1
common; pin 2 DC with channel 1 audio; pin 3
channel 2 audio)
Compatibility: single- and dual-channel intercom
systems such as from RTS® and Clear-Com®
Impedance – Normal: >10 k ohms
Impedance – 2-Wire (PL) Power Source Mode:
200 ohms
Nominal Level: –10 dBu
“Mic Kill” Signal: square wave, 24 kHz, ±1%
2-Wire Power Source: 30 volts DC nominal,
300 milliamperes maximum
Hybrids: 2
Topology: 3-section analog circuitry compen-
sates for resistive, inductive, and capacitive
2-wire party-line 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: >40 dB, typical at 800 Hz
4-Wire Inputs: 2
Type: transformer-coupled, capacitor isolated
Impedance: 13 k ohms
Nominal Level: +4 dBu
Maximum Level: +22 dBu
4-Wire Outputs: 2
Type: transformer-coupled, capacitor isolated
Impedance: 50 ohms nominal
Nominal Level: +4 dBu
Maximum Level: +20 dBu into 2 k ohms
Meters: 4
Function: displays level of 4-wire inputs and
outputs
Type: 5-segment LED, modified VU ballistics
Connectors:
4-Wire Line Inputs: 3-pin female XLR-type
4-Wire Line Outputs: 3-pin male XLR-type
2-Wire (PL) Interface: 3-pin male and female
XLR-type
External 24 Volt DC Input: coaxial power jack,
2.1 x 5.5 mm, locking bushing, compatible with
Switchcraft® S760K plug
Power Requirements:
External: 24 volts DC nominal, acceptable range
20 to 28, maximum required current 750 milliam
-
peres @ 20 volts. Universal mains input/24 volt
DC power supply shipped with each unit.
2-Wire Party-Line (when serving as source):
24 to 32 volts DC, 175 milliamperes
Studio Technologies, Inc.
Skokie, Illinois USA
[phone]
© by Studio Technologies, Inc., April 2011
studio-tech.com
Dimensions – Portable “Throw-Down”
Version (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-unit
(M45ARM-1), dual-unit (M45ARM-2),
or “1/2-rack” (M45ARM-3) rack-mount front
panels; single-unit and dual-unit panels use
one space (1U) in a standard 19-inch rack,
“1/2-rack” panel uses one space (1U) in a
special 10.5-inch rack
Weight: 1.8 pounds (0.82 kg), rack-mount front
panel adds 0.2 pounds (0.09 kg)
Specifications subject to change without notice.
4-Wire Interfaces
Associated with the 4-wire portion of the Model
45A’s interface are analog line-level inputs and
outputs. These are intended to interconnect with a
variety of 4-wire devices, including matrix intercom
systems, audio-over-fiber transmission systems,
and other specialized audio equipment. The input
and output circuitry is transformer-coupled to minimize the
chance that hum, noise, or “ground-loop” issues will occur.
The +4 dBu nominal level allows standard audio signals to be
directly connected.
The Model 45A contains four 5-segment LED level meters. Two
meters display the level of the signals being received from
the 4-wire sources and two display the level being sent to the
4-wire outputs. 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
signal flow in and out of the unit. Additional LED indicators are
also provided, offering a status indication of the party-line DC
power and auto null functions. Two other LEDs offer a direct
indication of what source is powering the Model 45A.
Pro Audio Quality
The Model 45A’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 passive and active filters the frequency
response 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 45A’s 2-wire DC power
source offers a unique level of performance; its ability to deliver
power while maintaining audio quality is simply unmatched.
Performance Flexibility
While the Model 45A is designed to directly integrate into typical
applications, it’s ready to support those “one-in-a-million” situa
-
tions too. To accomplish this DIP switches, located on the front
panel, allow selected features to be revised as required.
Simple Installation
The Model 45A uses standard 3-pin XLR-type connectors to
allow convenient interconnection. For flexibility, access to the
2-wire party-line intercom interfaces can be made using the
connectors provided on both the front and back panels. The
Model 45A is housed in a rugged yet lightweight aluminum
enclosure that is designed to be “road tough.” The Model 45A
can be used as a standalone portable unit for “throw-down”
applications. Three 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 or one unit to be mounted in
a special 10.5-inch rack.
The Model 45A can operate from power provided by the
connected 2-wire party-line circuit or from the included external
24 volt DC power supply. Its mains input source can range from
100 to 240 volts, 50/60 Hz allowing operation virtually anywhere
in the world.
Model 45A Back Panel