skip to Main Content

The Mythical POTS Advantage: Line Powered Phones

When conversation turns to a debate of VoIP vs POTS one of the common arguments in favor of keeping at least one POTS line is the idea that a plain vanilla phone doesn’t require AC power. It’s power comes down that very same POTS line from the phone company, so in theory  it  remains operational in the case of a power outage. This is fast on the way to becoming a myth.

The idea itself is not wrong. You could have a very plain phone on your POTS line, and it would work during a power outage. However, the simple fact is that at least in the US…almost noone has a simple line powered phone anymore.

Consider as supporting evidence the following photo:

My apologies for the image quality. It was taken with my Blackberry Bold…a superior phone, but inferior camera.

This pic was taken in a Target store near my home. My wife had asked me to pick up a couple of things on the way home. Since I was in the store I thought I’d check out the aisle where they sold phones. They had a selection of phones, mostly cordless, and every last one…corded or cordless… required AC power.

Herein lie the transformation into myth that I referenced earlier. Even if you have an analog line, it’s very unlikely that you have a phone powered by that POTS line.

This same situation can be seen at retailers from Best Buy to Fry’s, and Micro Center to Sears. The line powered analog phone has long been MIA at American retailers.

Should this be cause for alarm? Are we left exposed? Should there be new legislation?  Probably not.

The simple fact is that as we have become a more technological society this transition was essentially inevitable. Most people have cell phones, some have only cell phones and not home phone at all.

Those of us who still have home phones can use a simple UPS to provide power in case of emergency. Some people, most notably AT&T U-Verse users, get a UPS as part of their service. Their voice line will be sustained during a power outage.

When we had the late, lamented ION service from Sprint it too included a UPS built into the CPE (pictured below)

People who use other VoIP services may have to take more direct responsibility for providing such capabilities. As we have not had POTS lines since 2005 we’ve taken care to ensure that our core network and phones remain functional during any short power outage. Back when I established this blog that was one of the first strategies that I sought to share.

Can we now lay to rest the idea that a line-powered is a real benefit to the PSTN? If you don’t have such a phone it remains an unrealized benefit. If you’re providing a UPS to run your phone then you could also be running your network and using your VoIP service, as we do.

I’m reminded of the old boy scout motto…”Be Prepared.”

Nuff said.

This Post Has 17 Comments
  1. Michael,

    I think the huge benefit of PSTN (or should I say SS7 in this case?) is the universal dialing plan.
    You enjoy VoIP today is based on the fact that it connects to PSTN in order to call other users. This is also the reason why HD Voice will stay a niche until it gets a boost similar to what VoIP gained from PSTN (=a way to interwork and interoperate with it across networks).

    That power issue? Nice to have, but as you said, irrelevant in 2010.


    1. Curiously, what you describe seems only partly true. G.722 is in fact an aspect of the legacy PSTN, arising in the same era as ISDN. It’s based upon TDM roots. I’ve heard it said that it should be possible to pass G.722 encoded HDVoice calls over an SS7 network.

      In fact, people have done this for years. In the US it was not common as ISDN was not commonplace. The only places that I see it commonly used is in high-quality audio links for recording studios, TV and radio stations. Even in those applications it’s often being replaced by other, more current technologies.

      My take-away from this is that HDVoice need not be connected with IP transport. It’s possible in the TDM realm, and over SS7.

      1. regarding isdn and g.722:

        In the cisco document you can see the isdn-layer-1 protocol mapping.
        Incl. g.711a/u (which is the isdn standard transmission) g.721 and g.722.

        this would also fit to the hdvoice radio article:

        that isdn phone supported g.722 and a with other vendors inter-operable
        15-khz mode and even a 15-khz stereo mode over 2-isdn-b-channels. (mpeg2 layer 3).
        This was used for audio transmissions (radio stations).

  2. Michael,

    There’s a reason all my communications equipment (Rogers Home Phone modem and the associated DECT cordless base station, cable Internet modem, routers and FreeTalk Connect box go through UPS’s.

    Great to see you providing awareness that UPS’s are needed with today’s phone offerings of any kind.

  3. I still have a corded phone/pots line in the bedroom for 911 purposes. I have the minimum service $23/month. We use piaf running on a laptop for outgoing calls. But we don’t gab much.

  4. Many people I know still have some analog phone phones

    A regular ISDN line on a central switch can drive one phone (has to support it)
    without local power in an emergency power mode.

    Some modern “NG” phone lines in Germany are using VoIP infrastructure (which is
    transparent for the user, so he might not even be aware that he is using Voip).
    If his “black box=CPE” is unpowered his phone would also not work anymore.

    Having a UPS is a great idea, but also think of longer outages.
    Maybe a solar charger for your mobile phone is also a good idea.

  5. I’m one of those hold outs that still espouses the use of POTS. I have numerous SIP channels, a “land line” via my television cable service and a single POTS line. I won;t relinquish the copper, even if it is just one.

    The reason I remain unwilling to release the POTS line is because I live in Florida. When, not if, a hurricane or tropical storm blows through and knocks out the power, it can be days until the power is restored. By then my UPSes have died, my noisy generator is out of gas and my battery backed cable ATA is dead as well. But, my POTS line still has power.

    But, you are correct, most people fail to realize that their cordless phone base stations require power. But, unlike most people, I’ve accounted for that too.

    All the previously described lines feed into a trixbox. The POTS line gets there via a LInksys SPA 3000. This little jewel has a VoIP port to the trixbox and an FXS port that is connected to a $6 GE POTS phone. Under normal operation, the SPA routes the FXO calls to the trixbox and the GE phone is just another extension, though rarely used. But, when the lights go out, the SPA fails with the FXO and FXS ports bridged so the GE phone is then directly connected to the POTS line.

    VoIP goes down, cable land line goes down, and eventually cellular goes down (either due to lack of power or over load) but, POTS phone service remains available indefinitely as the local CO has battery backup and an big honking generator that runs it for weeks on end.

    This strategy has proven itself three times so far.

    1. That you still have a line-powered phone makes the strategy logical. Many people simply don’t.

      Further, our experience here in Houston has been that, given some consideration, voip services can work in such disaster recovery modes. We had DSL service throughout Hurricane Ike and the post storm recovery. Our IP phones worked throughout the period. We even had a cellular gateway as a backup trunk line, although I accept that most people won’t go that far.

      I have heard stories of people who lost their analog lines because, in this new era, the phone companies are not providing the same kind of battery & generator backup at all CO locations. Fuel for the generator can also be a problem.

  6. Don’t assume that because you have your SIP phone, network switch, and broadband modem all on UPS that you’re set for the next power failure. In one site we maintain, the cable system depends on pole-mounted powered equipment without UPS (it appears) since during the last power failure the LAN stayed up and the cable modem was powered up, but there was no broadband connectivity.

    B.T.W. – the ADSL service to the same site stayed up during the power failure.

    1. A local UPS is only part of the solution. We have redundant sources of IP (Comcast, Covad DSL. Sprint 3G) that are fully independent. We also have a SIP-GSM cellular gateway giving us a wireless voice trunk even if all IP connectivity is lost.

      In the wake of Hurricane Ike in 2008 we had everything running normally right after the storm subsided. As you noted, the cable ‘net access was dead, but the DSL remained functional throughout the period.

      We’ve yet to install the automatic standby generator, but that’s just a question of funding.

  7. Over in the UK, most of us are required to subscribe for a POTS line as a condition of receiving a broadband data service. The exceptions are people who can get cable, as opposed to xDSL service, but even these people do not greatly benefit from getting rid of POTS because of the way that the only major cable operator chooses to price its services (and anyway, it has a very poor reputation for reliability and customer service).

    Also, the service obligations on the POTS providers greatly exceed those imposed on broadband service providers, in terms of obligatory response times for service faults and so on.

    On top of that, cut-throat competition in POTS call pricing has greatly reduced the benefits to be derived from VOIP from a purely cost-driven perspective.

    I still have a couple of line-powered phones in a drawer, and won’t be getting rid of them unless and until the regulatory environment decouples POTS from xDSL provision.

    1. Here in the US it is possible to get what is called a “dry loop” which is DSL without an associated voice circuit. I have such service from Covad to backup my business class cable ‘net access.

      I was actually driven to the decoupled service by the ILECs inability to resolve a fault. When we had DSL & voice on the same line an incoming call (ringing) would cause the DSL circuit to drop for a few minutes. No combination of line filters could resolve it. In a fit of frustration I ordered the dry loop service from a CLEC to replace the SBC DSL.

      Not doing business with the ILEC (now AT&T) directly has since become a matter of personal/family policy. They’ll not get a dollar from us if we can help it.

      1. Michael, I had noted your hostility to AT&T elsewhere on your site, and had been curious to know what lay behind it!

        I love your site by the way. It truly is an informative and entertaining resource.

        1. There’s a long story behind my opinion of AT&T, going back about 13 years…and very nearly involving a law suit. That experience is filed under “institutional abuse of customers in the face of an administrative error.” We vowed to never again do business with AT&T.

          When SBC assumed the AT&T name we were glad that our Covad service was installed before the bills could arrive on AT&T stationary.

  8. This is perhaps a bit stale, but I thought I’d add my bit.  I live in the NC mountains, 17K wire feet from the local telco’s (TDS) nearest DSLan box.  I get both pots and dsl via buried copper.  My primary house phone is a Panasonic 2 line Detec 6.0 phone where the base unit will operate on telco battery on line 1, giving me a phone during most power outages. The base unit and my dsl modem, router, etc. are on a dedicated UPS and good for several hours so we have phone throughout the house until the UPS runs down unless I start the generator and switch critical circuits over to it. The dsl component frequently goes out intermittently during thunderstorms, but until last week, the pots has never failed.  Last week, we took an indirect lighting strike about 2900 wire feet from the house, fusing a number of pairs, blowing open several junction pylons and blowing the telco nid off a neighbor’s wall near the strike. Power was out for several hours and the pots for a while longer.  TDS was prompt about repairing the POTS outage – more prompt than they are with dsl problems. This may be due to the fact that POTS is under the jurisdiction of the state regulators who seem to be proactive while the dsl is under FCC jurisdiction.

Comments are closed.

Back To Top