Analog or Digital Phone Line?

We get this question a lot, especially from fax machine vendors, sometimes from credit-card terminal vendors as well.  They will generally tell the customer that their equipment doesn’t work well with digital phone lines, and they need to get an analog phone line.

All phone lines are both analog and digital.  The difference is: where does the conversion take place?  For a standard analog phone line (POTS – Plain Old Telephone Service), the conversion takes place at the Central Office (“CO”) operated by your local old-fashioned phone company.  The line from your fax machine to the CO is analog – it’s a pair of copper wires.  At the CO, the signal is converted to digital and transmitted via the PSTN (public switched telephone network), which uses the same underlying technology as the Internet to transmit the data to the CO nearest the destination phone or fax machine.  At that remote CO, it’s converted again to analog and sent along the final stretch (called the “Last Mile”) to the phone or fax machine or whatever is connected to that phone number.

With a VoIP system, the conversion also takes place at the other end of a pair of copper wires; the difference is, that other end is in your office.  It’s an analog adapter that converts voice signals to data signals and back again, very similarly to the way the phone switch at the CO does.

So why do so many vendors think you have to have a POTS line for a fax, postage meter, or alarm? Because many VoIP vendors do not do a very good job of configuring or conditioning their equipment to work properly with these analog devices. In fairness, that’s not a simple task. All of these devices require a real-time connection without gaps or static or echos. Getting that to happen reliably over the open Internet, which nearly all VoIP vendors use for their telephone service, is extremely difficult.

The best solutions use a combination of excellent end-user equipment, smart software, dedicated circuits (or at least VPNs – Virtual Private Networks) between the end user and the hosted services provider, and cleverly adjusted combinations of parameters at both ends to get the effect of a continuous real-time communication even when the underlying connection is not that way. The VoIP designer for one of the largest service providers told me “Fax is a dark art; it’s the occult science of VoIP.”.

Of course the bottom line is: it’s gotta work. So make sure your provider is either able to make your analog device communicate flawlessly over their VoIP system, or be willing to install a POTS line at no additional cost if that’s what it takes.

Why You Should Never Press “RESET”

Most network devices come with a RESET button.  Routers, wireless access points, some phones, switches – all of these and more.  It’s kind of natural for someone to press this button when they think there’s a problem with the device.  Sometimes a tech support person will tell you to restart the device, and pressing the RESET button looks like a way to do that.  Most field techs (including ours) make sure to have at least one Telecom Device Reset Tool (aka “paper clip”) in their tool kits.

So, why am I saying you should never press this button?  Let’s look at what the RESET button actually does.  A network device has a bunch of internal settings that control how the device connects to the network, how you log in to it, and the details of its operation.  As it comes out of the box, the device will have a collection of known, default settings that you can use to log in to it for the first time and configure it for your particular requirements.  These default settings are stored permanently in the device, and when you press the RESET button, they override any changes you may have made and reset the device to the “factory original” settings.

If a device stops working while it’s in service, it’s often because of a bug in the internal software.  The internal memory fills up, or the CPU freezes, or just one critical feature (like routing) stops working.   In those cases, rebooting the device will often clear up the problem temporarily.  If it really is a bug in the software, then it’ll happen again and again need a reboot.

Restoring the device to factory settings is very, very unlikely to cure these problems.  Unless someone just logged in to the device and changed the settings, the settings cannot be the cause of the device suddenly failing.  What does happen is that the reboot that occurs as part of doing the factory reset also clears the problem.  Temporarily.

But restoring the factory settings has another result:  all of the settings that configured the device for your network are now gone.  If those settings are the same as the default settings, then there is no point in pressing the RESET button,it won’t change anything.  If, on the other hand, the working settings are not the defaults, then when you press the RESET button you are wiping out all of the correct settings, which will prevent the device from working.  So, don’t ever press the RESET button, just reboot the device if that’s what you’re trying to do.  Unplug the power, wait a sec, plug it back in again.

Like any good rule, this one has an exception.  There is one situation in which it does make sense to push the “RESET” button.  You are an IT person (or you’re working with one), you cannot log in to the device (it’s frozen completely, or you don’t know the password), and you know how to program it correctly for the network it’s attached to.  If that’s not you, stay away from RESET!


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