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Not two, Software but four. 6P4C means six positions, four contacts---it could have six pins, but only four of the pins are actually populated. It's a little more correct, when speaking of the connector itself, to call it a 6P4C modular connector. Very little information is available concerning the Kodak Amateur Printers, but I believe the one below is an early model because it is more complex (more expensive to build) and the switching mechanism seems to be more finicky as to adjustment than other models. There's a little more detail to what goes on at the two ends of the line. It doesn't cost much more, but it gives the telco the opportunity to upsell you to a second line. I'll take the opportunity to eulogize the conventional copper pair, though, by going in to a bit of detail about how it actually worked. For the purpose of this article I am mostly going to describe the state of a fairly modern local loop, such as one connected to a 5ESS or DMS-100 digital switch. The connector used for modern telephones is often called RJ-11, although that term is not exactly correct in a pedantic way that rarely matters.

Today, you are allowed to purchase and use your own telephones. In your house, you have one or more telephones that you use to make and receive calls. Local loops are routinely in poor condition which throws things out of spec anyway, and then subscribers use all kinds of weird phones that are not always that well designed (the history of regulation of telephone instruments could fill its own post). The phone wiring in your house joins your phones in parallel with a device formally called a Network Interface Device (NID), but often referred to as the demarc or demarcation point. The local loop is fundamentally two long copper wires that go directly from your phone to the exchange. First, let's talk about the very general architecture of an analog local loop. You might expect some hefty ISO specification for analog telephone lines, but there isn't really one outside of equipment specifications published by manufacturers. The conventional "copper pair" analog telephone line is fading away.

Ultimately the move to digital voice is probably a good thing, as the abandonment of copper plant will kill off DSL in urban markets and make way for faster offerings---from telcos, usually PON. There is no difference between the two wires electrically speaking, but one or both wires will often feature some type of marking to make them more easily traceable over a distance. This distance varies greatly. Details often varied from manufacturer to manufacturer, and because Western Electric had a practical monopoly on the manufacturing of telephone instruments for many decades, it's pretty much the case that the "standards" for telephone lines in the US were "whatever Western Electric did," which varied over time. The FCC's requirements are basically to "keep doing whatever Western Electric did," and are often surprisingly loose. There is no clear distinction between an electric wire and an electric cable. This is the first place to look whenever there is a problem with your tankless water heater. Still, there is some logic to differentiating digital voice and VoIP: because digital voice service is offered by the operator of the underlying IP network, it benefits from QoS measures that general internet traffic doesn't.

On consumer internet connections, especially slower ones, digital voice is still likely to be more reliable than VoIP due to QoS policy. This type of service is usually branded as "digital voice." Historically this seems to have come about to evade VoIP's bad reputation; in the early days of Vonage and the charmingly sketchy, back-of-magazine-ad Magic Jack, VoIP products often delivered subpar service. Today, I think "digital voice" has mostly just become part of price differentiation for carrier-offered VoIP, since independent VoIP services tend to cost considerably less. Independent telephone companies initially had to use different conventions than Bell because much of the Bell telephone system was under patent; after the expiration of these patents they mostly shifted to doing whatever Western Electric did to benefit from the ready availability of compatible equipment. Since I'm powering a forestry machine outside of my main power station, what is electric cable I wanted to use efficient cabling to transfer power to the engines. I connected them to a Logger and Arboretum, and then wired up some Tin Cable from an LV transformer pulling off of my main power storage. So I thought I'd use Tin Cable because it's much cheaper than Glass Fibre Cable.