OK, some of you may see this is a thinly veiled way to boost sales of equipment or software. If you can't be convinced otherwise, then stop reading now.
Now, the rest of you smart people, here's my reasoning.
ISDN has been considered for over 15 years the gold standard for a voice actor's home studio connection to their client's studios. When it was developed the Internet existed, but we had no broadband access in our homes. At that time ISDN technology provided the fastest possible data connection mere mortals could access. Along came audio codecs, hardware devices that take analog audio and squash it down to digital information that will fit down a 128kb/s pipe. It worked well, it was state of the art, and many commercial and broadcast facilities invested in it.
For 10 years ISDN was king of the mountain, with no chance of being knocked off. But in the last five years high speed Internet access has become more ubiquitous, and new technologies have come along to dethrone the king. The advantage of using an Internet based system has always been flexibility and cost, but not reliability. It appears that the balance of reliability is starting to tip from ISDN to Internet.
My theory is based on a few factors. As of late more and more of my ISDN using clients are complaining of stability issues, dropouts, horrible blasts of noise, and increasing support challenges and costs for installation and monthly service. The TelCos, in the Los Angeles area Verizon and AT&T, clearly don't have ISDN users high on the priority list. Ordering the service is becoming impossible in some areas, finding someone to talk to when service outages occur is painful, and monthly rates only go up. Call at TelCo to order ISDN and you'll see where the acronym's interpretation "I Still Don't Know" came from. It's just not profitable enough for TelCos to promote the use of ISDN any longer, and it shows.
ISDN requires special systems to be in place outside of the user's building. It appears in the wall like a standard phone line, but what happens once that copper wire reaches the pole is completely unique to this system. There are network cards and switches that have been in service for many years, some of them completely dormant for extended periods due to a lack of user base. At least half of the orders I've had placed for ISDN have needed repair immediately upon fullfilment to be functional. These systems just get older and more neglected over the years, while the Internet backbone receives the focus and funding. It also seems more commonplace and accepted that ISDN codecs need to be rebooted and "futzed with" to get a reliable "lock" with the other user. We just get used to this over time, but there really should be no reason we have to deal with this.
Those of you who would be seriously put out if you lost ISDN service for more than a few hours, I seriously recommend putting a backup system in place. The technology that has done the most to establish itself in the voiceover industry as an ISDN alternative is Source Connect. For under $700 with iLok USB key you can install this software on any of your Windows or Mac computers. There are no monthly charges, no install charges, no long distance, and no per-minute fees when you connect to another Source Connect user. Even if you don't use it for 6 months, that one time you use it to bail out an ISDN fail will pay for itself immediately. If you are lucky enough to work with a Source Connected studio, be prepared for how incredible it sounds compared to ISDN!
There are a few catches to using Source Connect to replace ISDN. First, it can't connect directly to an ISDN codec. Internet and ISDN are completely independent of each other and don't speak the same language. If the client you are working with only has ISDN, you'll need to employ the services of a "bridge". One such service dubbed Out of Hear, created by DG Entertainment engineer Steve Nafshun, does nothing but ISDN bridging. His studio has four Telos Zephyrs connected to four ISDN lines, and multiple Source Connect accounts always at the ready to make your connection. Steve assigns you a pair of ISDN numbers to give your clients and agents, and a correlated Source Connect account. If your ISDN service goes on the blink, or you want to travel away from the confines of ISDN availability, call Steve and he'll patch you through. It's seamless for your ISDN using clients, only increasing the latency or delay by second or so.
Second, it does require at least a 300 kb/s upload and download Internet connection of good quality. While WIFI can work in the best of circumstances, Ethernet is highly recommended. Some hotels may only provide WIFI, so this can put you at greater risk for signal drops. Configuring the network may be required in some cases for a trouble free connection, but I've found it usually can make a connection without special setup like port mapping. In my point of view these are small prices to pay for a system that can be used anywhere in the world, with only a mic, USB interface, and lightweight laptop computer.
One of my clients, Pat Duke, decided to forgo installing ISDN completely when he relocated to Los Angeles a few years ago. Check out this video of his recent appearance on East West Audio Body Shop, as he describes his home studio and experiences using Source Connect.