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Installation Profile: Legislative Sound

Nov 1, 2007 12:00 PM, By Garret Maki and Rodrigo Ordoñez

Inside the U.S. Senate Chamber’s digital audio upgrade.

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SNMP technology and multiple GUIs located throughout the facility allow maintenance staff to monitor the status of every component of the new audio system (main control GUI pictured).


Facilitating preventive maintenance tasks is a key feature of the Senate Chamber audio system. All CobraNet I/O devices, control computers, NION DSPs, QSC power amplifiers, and Ethernet switches are monitored using SNMP technology. Multiple graphical user interfaces throughout the facility display the status of every component to the maintenance staff. The monitoring software is also tied to the SRS engineers' pagers, and it will alert them within seconds in the event of a failure. Python scripts were developed to process the monitoring information and provide detailed data, allowing support engineers to be highly efficient.

Additionally, it would not be desirable to find out about the failure of a microphone at the moment a senator picks it up in order to speak. Therefore, custom tests were also developed that allow operators to test system inputs and outputs on a daily basis.

One such test provides graphical feedback to the operator and engineers and indicates the proper operation of the microphones and loudspeakers at the senator positions. Another test reports the state of the predictive mic muting mechanism at each desk unit. Because of their graphical nature, these tests can be run from maintenance stations located outside the Senate Chamber and do not require displacement of maintenance staff.

Access to the audio software and GUIs is restricted according to user level. SRS operators are responsible for the daily operation of the system. They sit inside the Chamber any time the system is in use and perform minor adjustments, such as tweaking the master level and turning a senator's microphone on or off when necessary.

Although the system does not necessarily require any user interaction during use, an operator is always there to verify that things run smoothly. In order to do so, he or she is provided with a hardware control panel containing individual mute buttons for each senator, which can be relocated based on the actual physical position of a senator's desk. The panel also provides individual on/off controls for the auxiliary microphone and line inputs, as well as basic system health indicators.

A software GUI replicates the functionality of the hardware panel and offers control redundancy. In the event a senator forgets to return his microphone to its holder after use, the operator can override local control and mute the microphone remotely. If a microphone is picked up in preparation for a speech, the operator can place it on standby while the senator prepares to speak. Each microphone can be placed in seven possible states.

Using the scripting language Python, a high-level user management system was developed to complement the control and monitoring functionality provided by Peavey NWare software. It allows GUIs to remain open and connected but locked in functionality until the correct user information is entered. It also allows management of operators' shifts and preset recalls, as well as online modification of user permissions.

In addition to having access to all the monitoring functionality, support and maintenance engineers from the Senate Recording Studio are provided with a control and setup GUI that enables them to reconfigure the system for use in case of changes, such as the relocation of senator desks. Several other customized user GUIs are provided, including a display-only monitor showing the current active microphones for use by the video producers, signal dynamics metering pages, and advanced configuration screens. Because all of these user interfaces are managed by the audio DSP system, they can be accessed from any location in the facility that is connected to the Senate audio network.

While the upgraded hardware and software at the operator's position maintained the functionality provided by the original audio system, the upgrade eliminated external control engines by incorporating all mixing and control functionality into the DSP system. The operator's panel, previously processed using an external dedicated engine, is now controlled directly using custom scripting running on the NIONs. A JL Cooper control surface replaced a complex and underused broadcast mixer, allowing all broadcast mixing and routing to be performed by the digital audio system.

Python scripts were also developed to communicate with external hardware, taking advantage of the different technologies and functionality provided by each product, including SNMP, Telnet, RS-485, relays, and control voltage inputs. By working hand in hand with manufacturers, the need for an external control system was avoided, and all functionality was integrated to the DSP system.

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