I thought it used to matter, and I’ve got little plug testers that will show a yellow light if the wires are reversed. But is that an old problem or still a concern?
To my knowledge, if it is an analogue phone set, it doesn’t matter. If it’s a digital phone, it does.
I work in a network department and I had to move phones around a building (350+ employees) for 3 years.
Doing cross-connects to our PBX, analogue phones it didn’t matter, digital sets had to be straight through.
In a residential situation, I wouldn’t worry about it.
MtM
The last time I worked for a phone company–some years ago–yes, the polarity does matter. But there’s an easy way to check.
The sound generator built in to the touchtone pad requires that the line voltage have the correct polarity, that is, it needs a positive voltage on the positive terminal and a negative voltage on the negative terminal. If you have the line reversed, you’ll hear the dial tone when you pick up and you can receive incoming calls with no problem…but the touchtone pad won’t generate tones.
So, attach the line any which way then try to make a call. If the touchtone pad works, you’re fine. If it doesn’t, reverse the line connection.
I always figured that even modern cheap junk phones have a bridge rectifier or some such circuit to ensure correct polarity.
I know for a fact that I have had it backwards many times in my home (gee, was it the white with little orange stripes or orange with little white stripes…) and it didn’t matter a bit.
I work for a telephone company and took the basic Installation & Maintenence class last summer. They taught me that it does matter and the last step in insalling a phone drop is to check to verify the polarity.
It won’t matter for voice phones, but for data applications like DSL it does matter. I don’t know about fax, dial up or ISDN.
Since dialup modems and fax machines are essentially digital applications using analog media, they won’t care. ISDN (is anyone even using ISDN any more?) would probably not work with the incorrect polarity…
Many older touch-tone phones will not work properly if the polarity is reversed.
I found a really cool bakelite wall-mounted rotary phone from the 40’s that would be perfect for the garage. Will this work OK? I think it has two wires, I will need an adapter I suppose.
Should work. You won’t need an adapter so much as a way to splice wires together, since the modern phone system has changed little in terms of line voltages since early on. New phones today also use only two wires, but most jacks and residential wiring has four (two pair) so a second line can be easily connected.
This is also true of some newer phones (and dialup modems, as well). A few years ago, when I first moved down here to Virginia, the tech from Verizon wired my new line backwards, so I had to go down and reverse the pair in the NID (the grey box on the outside wall of the house where the drop line feeds in) because neither my phone or modem would dial out, even though I could hear tone. Musta been a rookie tech. :rolleyes:
Tone works because it’s AC (with a DC bias), but the DTMF circuitry relies on proper DC polarity to work.
You just need the two wires run to the phone. Usually, the internal terminals you need to connect the phone line to will be labled L1 and L2.
If it really is Bakelite, try to be reasonably careful with it - Bakelite is a bit on the brittle side, especially when it’s 65+ years old.