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Philosophical question: Why are modular analog station telephone cables wired in reverse?

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Philosophical question: Why are modular analog station telephone cables wired in reverse? One modular connector is wired straight and the other is wired in reverse. e.g. 1-6, 2-5, 3-4, 4-3, 5-2, 6-1

I do have the answer. It had to be inferred and not directly search-able which makes the question interesting?

Why would you want a straight wired modular to modular cable? I'll leave this more open, but still telephony related.

Analog telephones of the modern ERA are generally not polarity sensitive.

I never thought about why until recently.


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since this seems to be a 3-line connection, and POTS supplies 3-line connections over two pairs (the third line is a "phantom"channel), the goal would be to preserve the phase relationship of the pairs to avoid crosstalk between the pairs. another reason i can think of to wire the pairs in a specific way would only apply to DTMF phones from the 1970s, which used a transistor oscillator for the tones. if the line polarity were wrong, the DTMF oscillator wouldn't function. after deregulation, 3rd party phone manufacturers used the expedient of using a bridge rectifier to make the phone "polarity agnostic"


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4 wires could have been because of princess phones and thus 2 wires provided power. Prior to the 6P4C for the most part standard, 4-prong jacks were used. Still have some in the house.. The jacks and plugs are crummy. 4-prong to modular pigtails work much better.

Never had these https://www.newegg.com/Product/Prod...VVw4rCh0VMAzoEAQYAiABEgLZ_fD_BwE&gclsrc=aw.ds, but they probably would have been somewhat better.

I'd probably use a coupler to a modular pigtail made with one of the above. Less chance of getting damaged.

Still not the answer for why the cords are wired in reverse. One straight wired, one reversed wired.
Thanks for looking at the thread.


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the reason the wiring on 4 conductor cables is reversed is that wire order on flat cables remain the same, and the connector key remains the same relative to the flat cable (key on the bottom). other than Western Electric DTMF keypads (type 35), there are no polarity sensitive components in the standard phone sets made by WE (type 72 DTMF dials had a bridge rectifier to insure proper polarity for the transistor).

actually the 4 wires are usually 2 separate lines, with green/red being the first line, and blk/yel the second line. i ran a BBS system for many years, and the main phone line was the grn/red pair, and the modem was connected to blk/yel and had a separate phone number. on a phone line, the open circuit (on-hook)voltage is between 32 and 48V, and the off-hook voltage about 6V. if required, a 3rd line can be connected using what's called a "phantom line", where you have a pair of transformers (called "hybrids"), and the 3rd line is provided by a differential current between the two physical pairs.
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There is a really good reason. Take a look here: https://www.onlineromania.info/old-telephone-wiring-diagram/ which has some typical wiring diagrams of telephone sets.

Inside the phone the quad wire colors are used for TIP and Ring which are the same colors used everywhere else.

Older phones had jumperable options especially for "party lines". My grandparents had them.

So, the flip or "reverse" wiring allows you to maintain the tip/ring colors throughout the system EXCEPT for that station to wall cord. So, it's pretty slick.

With direct wiring and 4-prong wiring (one end fixed) it was still possible to maintain the color coding within the phone, not the pin numbers of the cable. Reverse wiring does the same thing.
It also means that there is only one style "pigtail" (modular to wire),

"propreitary" digital phones require straight-thru cables. I don't know about VoIP phones.

Telephone patch cables need to be straight-thru wiring.

I will be doing some re-wiring of the house phones. there is like 3 demark points:
1) The NID
2) At the carbon surge protector inside the house
3) Junction box - center of the house

The mix of (2) and (3) and #1 for that matter was done by the phone company.

The house, (1960's) came with one hardwired desk phone. Later, 2 phones and three 4-prong jacks and an external bell were added by the phone company. Ringers were disconnected so the phone company didn't know of other phones. The 2 phones were "rented" and later purchased.
A "ringer" was installed in the cellar.

When modular was introduced, a lot of the locations have both modular and 4-prong.

Some alternate issues were in no particular order were:
1) Support a modem in the recreation room (modular)
2) Support a phone on the porch. 4-prong+modular (now a 4-prong to modular pig-tail)
with a 4-prong phone)
3) Support a 802.11b PPP over modem router.
4) Support a modem/phone in my "shop"
5) Support a phone in another bedroom
(I think support is removed right now. Low voltage plate installed - unconnected)
6) Modular support a PERS alarm and 4-station cordless phone and ANS machine.
This is now on a UPS. So, bedlamp, base station and PERS are on a UPS)
7) Support a wired phone in bedroom as well as cordless.
8) Support a ringer in the laundry room.
9) Support DSL
10) Support a big button touch-tone phone for hard of hearing in kitchen.
11) TV needed a phone jack. (now used by phone line monitor) it's also CAT3 - not good.

There was a "force" to support touch-tone because of banking. Then a force to go to a speakerphone because of the long wait times and everyone being hearing impaired a bit.
Either old age or in my case tinnitus at 2600 Hz.

The need for separate ringers has largely been replaced because 4 cordless phones is the basic need. Basement, bedroom #1, Bedroom #2 and Living rm.

A 2-parent "baby monitor" was added with the child monitor in the basement that amplifies the cordless phone ringing. The laundry and my bedroom get the parental units and the paging function is used extensively since mom is bed bound. The UPS was a big addition because you never lost the time or messages on the answering machine. Ni-mH batteries increased talk ans standby time tremendously. The second parental baby monitor is in my bedroom.

The "latest" addition was an "off hook-solid", "ringing-some cadence" and "disconnected-fast cadence LED. I'm still trying to find the best LED to use at the top of the flat screen TV.

What I was really looking for was "off hook and not talking for say 15 minutes" as well as ringing.
It's now easy to put the phone off hook, so the light has been invaluable. Might really want something like: 1) Steady RED off hook for some time; 2) Fast blink RED disconnected; 3) Green blink (some cadence) - phone ringing; 4 Yellow - optional (off hook - short delay (like 10s).

Making the PERS to do line siezure would be nice. The base needs to be moved too or a remote mic added. Two pendants should really be used where the monitoring service either 1) Calls hospice; 2) calls 911 medical depending on which is pressed.

Missing pieces to the entire need includes: 1) Remote door unlocking; 2) Video doorbell and 3) Vertical blind control.

Aside: I really want to do put in place a comprehensive sensor monitoring system. This https://www.monnit.com/ is so far the coolest, but it has issues too. In some cases, it might take 10 minutes to know about a flood. I have lots of questions. Water, refrigerator, freezer, door prop, smoke fire etc.

I have a 12 port RJ45 panel for phone where everything will be bridged and a 48 CAT6 RJ45 port to premise wiring panel in place. I have a 24 port POE switch that I need to install.

Any new premise connections will be CAT6 RJ45. If they are phone, the wall jacks will get inserts. http://www.l-com.com/ethernet-modular-8x8-insert-adapter-pkg-10. Not sure how to handle the patch section. RJ45 cable color and labels or inserts and RJ11 cords. That will help bunches.

Sorry for the rambing. Again, thanks for responding.
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I really want to do put in place a comprehensive sensor monitoring system
If you also want a good security / home automation setup, have a look at the HAI / Leviton Omni security systems.
You can set any zone as various alerts like flood etc. as well as security and fire.

The number of zones depends on the system version, from 24 to 176 I believe. It will bleep at the alarm keypads, sound an alarm and phone a list of up to eight numbers when triggered, giving the address and if you enter the code, it will read out the exact zone(s) triggered and by what.
You can phone in to them if you configure it that way, plus there is a phone app for remote monitoring and control.
And they have a mass of other features from Z-wave through whole-house audio etc. available.

The smallest one (Omni LTe) goes very cheap on ebay, the top Omnipro II is $1000+..

List of zone types from the manual for my Omnipro:

ENTRY/EXIT 0 Entry/Exit
PERIMETER 1 Perimeter
NIGHT INT 2 Night Interior
AWAY INT 3 Away Interior
2X ENTRY DELAY 4 Double Entry Delay
4X ENTRY DELAY 5 Quadruple Entry Delay
LATCH PERIM 6 Latching Perimeter
LATCH NIGHT INT 7 Latching Night Interior
LATCH AWAY INT 8 Latching Away Interior
PANIC 16 Panic
POLICE EMERG 17 Police Emergency
TAMPER 19 Tamper
LATCH TAMPER 20 Latching Tamper
FIRE 32 Fire
FIRE EMERG 33 Fire Emergency
GAS 34 Gas Alarm
AUX EMERG 48 Auxiliary Emergency
TROUBLE 49 Trouble
FREEZE 54 Freeze
WATER 55 Water
FIRE TAMPER 56 Fire Tamper
AUXILIARY 64 Auxiliary
KEY SWITCH 65 Keyswitch Input
ENERGY SAVER 80 Programmable Energy Saver Module
OUTDOOR TMP 81 Outdoor Temperature
TEMPERATURE 82 Temperature
TEMP ALARM 83 Temperature Alarm
HUMIDITY 84 Humidity
ER OUTDOOR TMP 85 Extended Range Outdoor Temperature
ER TEMPERATURE 86 Extended Range Temperature
ER TEMP ALARM 87 Extended Range Temperature Alarm


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sounds like you have a bit of a project ahead of you. also sounds like the 2.4Ghz band is going go be a bit cluttered with wifi+cordless phones.

Older phones had jumperable options especially for "party lines". My grandparents had them.
there were actually two different methods of setting up party lines, series and parallel. i was unknowingly connected to what must have been a party line. i had moved into a rooming house, and i connected up a phone i had. i used one of the test numbers (number readback) to get the phone number. i used the phone for several months, assuming it was owned by the rooming house. until the phone rang one time, and it was somebody i didn't know. i found out the line belonged to somebody who lived several blocks away. this was in North Carolina in the late 1970's. i thought it was caused by some mixup at the phone company, but realize now it had probably been a party line at some time.

using all RJ45 jacks with RJ11 adaptors will allow you to replace an analog phone with a voip phone or network connection in the future without leaving dry copper in the walls ("dry copper" being telecom-speak for unused wires).

you have likely noticed that the modular connectors always have a symmetrical pinout, even for the cable from the phone to the handset. modular connectors as used in telephone service appear to have been well thought out, as any 4-wire RJ11 cable could be used for connecting the phone to a wall jack, or connecting the handset to the phone.

"propreitary" digital phones require straight-thru cables. I don't know about VoIP phones.
VOIP phones use standard network connections. VOIP phones without a wall wart require POE (power over ethernet) connections. some VOIP phones also have a shared connection, so you can connect a computer's network cable to the phone, and the computer and phone are actually running off an ethernet hub in the phone. this gives the phone and the computer separate IP addresses, but you only need one wall connection.

if you are installing a bunch of computers and VOIP phones, i recommend you do everything with static IP addresses rather than DHCP. use either blocks of IP addresses for different devices, or use a numeric scheme. for instance, all of the computers would have IP addresses in the to range, VOIP phones in the to range, another block for wifi devices, and another block for printers, etc... these would be examples of using designated blocks of ip addresses, or you could do it numerically where IP addresses ending in 1 would be computers, ending in 2 for phones, ending in 3 for wifi, etc... so a computer would be at or .21 and a VOIP phone would be at or .12, connections to cell phones on wifi would be at, or .13.

the difference between using the blocks and numerics is that you would get 24 blocks for 24 different types of devices, or 10 numeric groups for 10 different types of devices. personally i use the numeric groups. all computers are on a group all ending in the same digit.

if you have devices that you want to isolate from other devices in the network (for instance, you don't want to allow the VOIP phones to be reachable by any computers in the network) you can also use a limited subnet and a separate router (not referring to the DSL modem as a router in this context). for instance you add a router, and set it to use the DSL modem's gateway at (this will be the router's "external" connection), then for the router's "internal" network you set the subnet mask as the router's "internal" address would be (this would also be set as the "gateway" address on all of the phones), and all of the phones would have IP addresses between and this gives address space for 14 phones. this would also be ideal for IOT devices because it prevents the IOT devices from being useful to attack the network because the subnet mask only allows 16 addresses within the network, so an IOT device can't talk with anything outside it's subnet, but it still can reach the internet. the best way to use such a scheme is to segregate the network into two sections, each with a separate router downstream from the DSL modem. partitioning the networks so that the IP addresses of all the computers, printers and wifi devices are below, and all the IOT and phones are above .127 (with a subnet mask of 255.255;255.128). the subnet masks would not allow traffic between the two segments. if management of the IOT devices is required, a computer can be connected to that network for that purpose. i'm thinking that my first thought of only restricting the subnet of the IOT devices and not restricting the remainder of the network may have some flaws in it, but i'll have to test it to find out. i have a few spare routers and a few raspberry pi computers to test with.


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I found something really interesting about the origins of the telephone system. It looks at the development in a specific area. So far, it has been a good read: http://atlantatelephonehistory.org/atlanta:start

My uncle had a princess phone where the second pair contains a power supply that was in the house for the lighted dial.

I do remember trying to find the Bell Tell journal about the "Blue Box", but it was pulled from the collection. I only learned later that whistles suppied in Captan Crunch Cerial were tuned the 2600 Hz, the disconnect tone. I do remember when long distance calls were preceeded by a bunch of tones.


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I found something really interesting about the origins of the telephone system. It looks at the development in a specific area. So far, it has been a good read: http://atlantatelephonehistory.org/atlanta:start

My uncle had a princess phone where the second pair contains a power supply that was in the house for the lighted dial.

I do remember trying to find the Bell Tell journal about the "Blue Box", but it was pulled from the collection. I only learned later that whistles suppied in Captan Crunch Cerial were tuned the 2600 Hz, the disconnect tone. I do remember when long distance calls were preceeded by a bunch of tones.
that was a secondary use of the other pair, which was usually available inside the house because most people could only afford the one phone line.

yeah, the Capn Crunch whistle was a fluke, and the maker of the toy must have thought the sudden popularity of it was a marketing coup, and probably didn't have a clue at first why. the 2600 hz tone was used for "hook flash" and could be used for seizing trunk lines for long distance calls. when i was a kid, and before there were touch-tone dials, i found out there was a dial switch inside the rotary dial, and as long as you never let the dial go back to it's rest position, you could add more dial pulses than 10. i must have tied stepper relays up in knots playing with that. i got some interesting results running the steppers through more than 10 steps. i'm not sure how the steppers interpreted the extra pulses, and i think i often got the "reorder" error signal. i did discover some interesting numbers. in some exchanges dialing 2002002002 would get two ringing signals, a click, and then a dial tone, and long distance calls could be made without charges. in one exchange, the number was 4004004004.. when i was a kid, i knew several test line numbers, the one that read back the number for the line, and the one that would ring the line back after you hung it up were both useful (the ringback one was great for pranks where there were extensions).

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In the old days, when only pulse dialing was used, we found out that you could make free calls from the call box in our village. There was only one call box, and only a VERY small number of private phones back then - I only knew of five or six - and I doubt it made much above double figures :D

Anyway, on the very old Post Office call boxes you used to have two buttons A, and B - and in order to dial out you had to put money in first, and if there was no reply you pressed button B (I think it was B?) and you got your money back.

We found out that you could dial out without money by picking the handset up, dialing a digit, and hitting the handset rest at the correct speed while the dial whizzed back round. Obviously, this was VERY prone to wrong numbers, as it depended entirely on the accurate timing of pulsing the rest. But as we had no one to call (no one much had phones) it didn't matter as long as you got someone :D


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Some where I ran into a phone with a dial lock on the phone, so I dialed it with the switch hook.

A friend and I used to use a computer terminal for a long time with an acoustic coupler attached to a pay phone. 99% of the time we would get our money back.


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if you ever wonder about why pay phones use spiral steel armor on the handset cord: the original coin switches on pay phones operated by switching one of the wires in the handset (most likely the microphone wires, since they had battery voltage on them) to the faceplate ground. people figured this out and would use sewing needles to flash the coin switch, each click was a nickel. then they armored the cables so nobody could stick a needle into the wires. later they started using tones for the coin switch, and so there was one of the colored boxes invented to send coin tones.

when i was in the Army, they began using touch tone field phones. there were 16 buttons on the dial. one of the buttons was an override button, that would sieze a line on the civilian phone network if civilian phone networks were near capacity. apparently it was used quite often during field exercises. if you lived in one of the local towns around an army base, every once in a while you could be talking to somebody on the phone, and the call would disconnect. what? field phones connected into the civilian phone network? yes, on long field exercises they would have soldiers phone home to let family know they were ok...


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Kinda did that once to get onto a computer system that had only a small amout of lines/users. Asked to verify the line and you could size ir.


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i used to have the "big blue book" that was the phone installer's manual. it was given to me by an installer that came out to fix a problem with the line. when you are a 10 year old kid with a lot of curiosity, you can get a lot of cool stuff... well, at least you could back then... these days they probably have the installers sign for the book and have them guard it with their life... when i was 12, i picked up a lineman's handset at a garage sale, that thing was a lot of fun... you would be surprised how many "live" lines you can find that aren't being used for anything in old buildings. i worked for a while as an alarm installer, and i would use that handset to find the phone line for the alarm system using the handset to dial the line that read back the number. i would find lines that weren't connected to anything else, and probably hadn't been in a long time, but were still connected to the block, and still working.
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