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Wheatstone’s SwitchBlade Addresses ISDN Challenge

iHeartMedia needed to settle on companywide codec/installed audio network solution

CLEVELAND — ISDN is out, audio over IP is in.

Major telecom companies have announced plans for the sunset of ISDN and the service has been terminated by several providers in the U.S. in the past 18 months.

In place of ISDN is a wide variety of audio over IP solutions. Even though AoIP has moved studios into the IP realm, converting that IP audio into a routable codec solution has been a clunky bolt-on solution. In many cases, broadcasters have had to resort to running separate codecs or software on computers in the studio with sound cards wired directly into the console.

By 2016, VoIP was making an enormous difference in corporate telecommunications, both in terms of speech quality and in the range of services available. SIP was already being implemented across different codec manufacturers for interoperability, so a solution of SIP-enabled codecs combined with the Opus open source codec seemed to hold the promise of being a reasonable replacement for ISDN distribution.

[Read “How to Choose Your Next Console”]

We were looking for a way to take WheatNet-IP audio in our studio facilities and seamlessly integrate bidirectional codec functionality into the architecture. The ideal solution would operate natively in both environments — presenting fully-connected AoIP channels on the studio audio side and functioning as fully-featured AoIP SIP/Opus (VoIP) codec for audio connectivity outside the studio facility.

Nothing like this had been developed before, so we enlisted the help of Wheatstone and its partner Radiomation, an Irish company that had already been doing pioneering work linking Wheatstone equipment to existing ISDN and POTS telecommunications equipment.


The result was SwitchBlade, an AoIP appliance that seamlessly integrates 24 remote AoIP connections directly into the WheatNet-IP audio network at the studio. SwitchBlade is a single 1RU unit chassis with a 24 software codecs routed to any source and destination on the WheatNet IP-Audio system.

By the end of October 2017, SwitchBlade had been demonstrated as a proof-of-concept at the iHeartMedia Engineering facility in Cincinnati. After NAB in 2018, SwitchBlade’s next stop was the iHeartMedia studios in Cleveland, where we performed beta testing and drove further development, resulting in a widespread deployment across iHeartMedia in 2019.

SwitchBlade has allowed iHeartMedia to proactively migrate away from ISDN to audio over IP for remote audio connectivity. Standardizing on the open standard of SIP for initiating the connection, and the wide adoption of the open source Opus codec, has resulted in interoperability with many different existing codecs in the field.

SwitchBlade has the intelligence to be controlled using all the WheatNet-IP programmability. All 24 internal modules can be individually controlled by custom console interfaces; the Wheatstone ACI; ScreenBuilder, Wheatstone’s widely-used programming environment; and integration into RCS NexGen and other automation systems for automating the various remote AoIP connections for each show.

Among the many unique qualities of this appliance is its ability to dynamically assign and pass any of 78 GPIO closures, and have serial network cues associated with satellite-delivered program travel with the program audio, arriving at the remote end still perfectly synchronized with the content. This was achieved by embedding the signals directly into the audio stream so that signals and content are always perfectly synchronized regardless of any delays to the signal path.

[Solving the Missing Link]

Being driven by the iHeartMedia Engineering team for the past two years has made SwitchBlade into a world-class solution — a fact recognized by the National Association of Broadcasters, which gave it the “Product of the Year Award” in the Audio Production, Processing and Networking category at NAB Show 2019.

SwitchBlade has not only met and exceeded the “ISDN-Replacement” challenge, it has changed our thinking on everything from satellite program distribution and telephone contributions to inter-facility content distribution.

For information, contact Jay Tyler at Wheatstone in North Carolina at 1-252-638-7000 or