I think we can now foresee the demise of traditional telephone service delivered over the PSTN (public switched telephone network). My best guess is the PSTN will ether be dead or dying by the end of 2030. This doesn’t mean the death of telephone voice service, but the end of the regulated service that has been offered by telephone companies. Any voice products that remain will be delivered using VoIP.

The death of the PSTN is being fostered by the FCC, which has made it much easier for telephone companies to tear down or decommission copper telephone networks. The FCC began the process by providing a two-year moratorium on notifications for taking down copper in July and followed that up more recently with a formal docket to make the rules permanent.

Eliminating copper lines is not the same as eliminating the PSTN. I expect the FCC will formally announce rules to end the PSTN soon. But even if the FCC doesn’t take specific action, I expect the big telcos to start dismantling the PSTN in pieces on their own.

The PSTN consists of a private network owned collectively by telephone companies. The PSTN is a series of regional networks that surround a large tandem switch that connects to the telcos and CLECs in the region. The connections between each voice provider and the tandem are called trunks. These are transport routes, many still using the old TDM technology based on T1s, to deliver the traffic. Local voice providers can also have direct trunks to other local voice providers in the area, to the largest long-distance carriers, or to the large cellular carriers.

The PSTN is also the mechanism used to route calls between a local voice provider and the many other carriers in the country. There is a complex set of routing tables that instruct tandem switches how to route calls to reach every registered telephone number in the system. The PSTN is also the starting point for routing other kinds of calls, like international long distance and 800 numbers.

This may sound too complex to break apart, but the biggest telcos have been talking about this for over twenty years. They do not want to be responsible for taking care of the local PSTN arrangements, which costs them money and causes a lot of maintenance. I remember sitting in meetings twenty years ago that discussed ways that the regional tandem switching network could be deactivated over time. There was a lot of investigation done on the topic ten years ago at the FCC, but that effort fizzled out somehow.

The impetus to dismantle the PSTN was always driven by money. The big long-distance carriers were paying huge amounts in access charges to get ‘access’ to the local networks of the many voice providers in the country. The FCC took an axe to many of those fees, and after the magnitude of spending on access decreased, I think the focus on finishing the process died.

The largest telcos like AT&T have always envisioned a much-simplified replacement for the PSTN. Twenty years ago, AT&T talked about a vision where it would replace hundreds of tandem switches nationwide with perhaps two for the whole country. Every carrier that used one of its tandems would be responsible for buying transport to reach one of the big new switches. We can’t ever get rid of the function of routing calls, but this vision would shift most of the cost of the PSTN function away from the big telcos onto each company that originates or terminates voice calls. Under the AT&T vision, the PSTN would be greatly simplified by greatly decreasing the number of locations where calls are exchanged.

There is nothing stopping the big telcos from doing this, other than having a method in place to make sure that calls continue to route. The big carriers are feeling emboldened by the current FCC to wash away old systems, and I think they are now ready to finally tackle this.