Studio Technologies Model 45A Interface Details
Studio Technologies Model 45A Interface is designed to interface a 2-wire full-duplex party-line intercom circuit with a 4-wire audio circuit associated with a matrix intercom system. Other specialized audio system interfacing applications can also be supported. Applications for Studio Technologies Model 45A Interface include television sports and special event broadcasting, theme park and theater installations, corporate events, and industrial testing environments.
Studio Technologies Model 45A Interface provides a full-featured 2-channel interface which includes two hybrid circuits with automatic nulling capability. The analog hybrid circuitry provides excellent audio quality and high return-loss. For flexibility, Studio Technologies Model 45A Interface can be powered by the connected 2-wire party-line circuit or by means of an external source of 24 volts DC. When powered by an external source Studio Technologies Model 45A Interface is capable of supplying DC power to the 2-wire intercom circuit, allowing direct operation of devices such as user beltpacks. Audio level meters provide confirmation of system performance during setup and operation. Standard audio connectors are used for all input and output signals. Studio Technologies Model 45A Interface's enclosure has a "1/2-rack" 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 Studio Technologies Model 45A Interface units can be mounted in a single space of a standard 19-inch rack enclosure or one unit can be mounted in a special 10.5-inch rack.
Studio Technologies Model 45A Interface's 2-wire interface is optimized for direct connection with dual-channel party-line (PL) intercom circuits such as the TW-Series of intercoms from RTSÂ®. In addition, other industry-standard single- and dual-channel PL intercom circuits, including those from Clear-ComÂ®, are compatible.
Studio Technologies Model 45A Interface's 2-wire interface can correctly function with powered ("wet") or unpowered ("dry") intercom circuits. An auto-terminate function ensures that should a "wet" circuit not be connected, Studio Technologies Model 45A Interface's interface circuitry will remain stable. This unique feature makes certain that objectionable audio signals, including oscillations and "squeals," won't be sent to the connected 4-wire device.
A significant capability of the Studio Technologies Model 45A Interface's 2-wire interface is its ability to supply DC power and 200 ohm AC terminations to "create" an intercom circuit. The 30 volt output can power a limited number of devices such as user stations and beltpacks. With up to 300 milliamperes of current available, a typical broadcast application that uses two or three BP325 beltpacks can easily 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.
Analog Hybrids with Auto Nulling
The 2-wire-to-4-wire hybrids provides low noise and distortion, good frequency response, and high return-loss ("nulling"), even when presented with a wide range of 2-wire conditions. Unlike telephone-line ("POTS") oriented DSP-based hybrid circuits, Studio Technologies Model 45A Interface's analog circuitry maintains extended frequency response. With a pass band 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 2-wire party-line circuit.
Studio Technologies Model 45A Interface's sophisticated auto nulling function uses analog circuitry under microprocessor control to achieve significant trans-hybrid loss. This return-loss "null" is achieved by making a series of software-directed adjustments to account for the resistive, inductive, and capacitive conditions that are present on the connected 2-wire party-line circuit. Whenever a user presses Studio Technologies Model 45A Interface's auto null button digital circuitry adjusts the analog hybrids to achieve their maximum return-loss for both interface channels 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.
Associated with the 4-wire portion of the Studio Technologies Model 45A 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.
Studio Technologies Model 45A Interface 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 Studio Technologies Model 45A Interface.
Pro Audio Quality
Studio Technologies Model 45A Interface'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, Studio Technologies Model 45A Interface's 2-wire DC power source offers a unique level of performance; its ability to deliver power while maintaining audio quality is simply.
While Studio Technologies Model 45A Interface is designed to directly integrate into typical applications, it's ready to support those "one-in-a-million" situations too. To accomplish this DIP switches, located on the front panel, allow selected features to be revised as required.
Studio Technologies Model 45A Interface 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. Studio Technologies Model 45A Interface is housed in a rugged yet lightweight aluminum enclosure that is designed to be "road tough." Studio Technologies Model 45A Interface can be used as a stand-alone 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.
Studio Technologies Model 45A Interface 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.
Studio Technologies Model 45A Interface Features
- Portable "throw-down" or rack-mount use
- Analog hybrids with auto null capability
- Input and output level metering
- Excellent audio quality
- Flexible powering
- Standard audio connectors
- Transformer-coupled 4-wire inputs and outputs
- Integrated 2-wire intercom power source
Studio Technologies Model 45A Interface Specifications
- Manufacturer: Studio Technologies
- Product: Model 45A Interface
- Frequency Response: Â±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 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 RTSÂ® and Clear-ComÂ®
- Impedance-Nominal: >10 k ohms Nominal
- Impedance-2 Wire (PL) Power Source Mode: 200 ohms
- Nominal Level: â?"10 dBu
- "Mic Kill" Signal: Square wave, 24 kHz, Â±1%
- 2-Wire Power Source: 30 volts DC nominal, 300 milliamperes maximum
- Hybrids: 2
- Topology: 3-section analog circuitry for resistive, inductive, and capacitive 2-wire party-line loads
- Nulling Method: Automatic upon user initiation
- 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
- Inputs: 2
- Type: Transformer-coupled, capacitor isolated
- Impedance: 13 k ohms
- Nominal Level: +4 dBu
- Maximum Level: +22 dBu
- 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
- 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 SwitchcraftÂ® S760K plug
- External: 24 volts DC nominal
- Acceptable Range: 20 to 28 volts DC
- Max. Required Current: 750 mA @ 20 volts
- Universal Mains Input: 24 volts DC power supply shipped with each unit
- 2-Wire Party-Line (when serving as source): 24 to 32 volts DC, 175 milliamperes
- Width: 8.7 inches wide (22.3 cm)
- Height: 1.72 inches high (8.9 cm)
- Depth: 8.3 inches deep (21.3 cm)
- Weight: 1.8 pounds (0.82 kg), rack-mount front panel adds 0.2 pounds (0.09 kg)
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