Wall plug wires? [telecom]

On an old Princess phone here, red/green are ring/tip and yellow/black are for 6 VAC (from a Bell Co. wall-wart) for illuminating the phone's lamps.

According to the wikipedia page / anchor

:

: Pins 2 and 5 (black and yellow) may carry low voltage AC or DC power. : While the phone line itself (tip and ring) supplies enough power for most : telephone terminals, old telephone instruments with incandescent dial : lights in them (such as the classic Western Electric Princess and Trimline : telephone models) needed different voltages than the phone line supplies. : Typically, the power on Pins 2 and 5 came from a transformer plugged into : a power outlet near one jack, wired to supply power to just that telephone : (or to all of the jacks in the house, depending on local ... practices).

I'd be very shocked to learn the yellow/black were meant for 120 VAC ... very shocked indeed (double entendre intended) :-) . Cheers, -- tlvp

The Y/B pair could also be used for:

RJ-14 = 2 pots lines in one jack

RJ-48 = Receive pair of a 4 wire T-1/DS-1 circuit or subrate DDS

Receive pair of a 4 wire analog modem circuit (Type 3002)

*******************************************************************

• Moderator Request *

• *

• If you want your post published anonymously, please put the *

• "[anonymous]" tag in your subject line, and send your post *

• from a valid email address! If I can't confirm that *

• you're a real person, I won't take your post seriously! *

• *

• Please read the F.A.Q. for more info on this! *

*******************************************************************

Outstanding link.

Thank you.

Other research has indicated the black/yellow from the telephone pole is for a second circuit. I assume all current wall socket pins are all connected in parallel and to use the second circuit at a particular phone I would have to move/jumper the black/yellow wires to the Tip/Ring (red/green) pins on that particular socket.

If that assumption is correct I will not have to snake any wire back to the outside junction box. :)

This research is for the possibility that a friend's house alarm is wired in series between telco and house wiring.

If alarm is in parallel, nothing has to be done except remove telco drop, plug Cisco SPA122 into wall socket and alarm and other phones would be running through the SPA122.

If alarm is in series I have to get SPA122 tip/ring back to junction box. In that case I think I can get away by using black/yellow pair. :)

In either case he will be able to drop that monthly phone bill to around $30 a year.

Keep in mind all wiring [advice] is [saying] "This is how it SHOULD be wired" which isn't always reality.

Normally, alarm systems are installed in series with the house wiring at the front of the line. The reason is to prevent a burglar from entering, taking a phone off hook, dialing some busy number, and preventing the alarm system from calling its destination. By being in front in serial, the alarm system can cut off all the other phones. Smart burglars could get around this, of course, but this is only to thwart halfway-smart burglars.

Also, some alarm systems need a special adjustment when they are unhooked from a genuine 100% POTS phone line. Check with the alarm company, and be sure to test the system after any changes.

Anyone who was running a T-1/DS-1 over D type wiring should be drawn, quartered and then shot. The cross talk would be something awful in that type of wire and do stuttering wonders for a data circuit.

The alarm system interface is USOC RJ-13X defined in 47 CFR 68.502(b)(1). As

+--------------------------------------------------------------+ 68.502(b)(1) Series T/R ahead of all station equipment: 8-position series jack. Electrical Network Connection: Series tip and right ahead of all station equipment. Conductors 2,3,6. and 7 are reserved for telephone company use. Universal Service Order code (USOC): RJ31X. Mechanical arrangement: Miniature 8 position series jack. Wiring Diagram: (wiring diagram appears on the following page) +--------------------------------------------------------------+

Source: FCC Rules and Regulations (1997), Part 68 - Connection of terminal Equipment to the telephone Network. A Copy of the 1997 edition of Part 68 is posted at:

The text quoted above appears on page 397 (PDF page 137/157).

The wiring diagram appears at the top of page 398 (PDF page 138/157).

The 1997 edition of the FCC Rules is the last edition in which the FCC published wiring diagrams. Since 1998, wiring diagrams have been published by the Administrative Council for Terminal Attachments.

Neal McLain

Older model Princess and Trimline sets had a tiny incandescent lamp to illuminate the dial* when the phone was in use. As mentioned, this was powered by a small plug-in transformer. This was for illumination only and was not necessary in the regular use of the telephone set.

If only one telephone set was powered, usually a power outlet near the phone was utilized. However, if multiple sets within a home were powered, then a transformer was plugged in a central location.

Many years ago an alert went out for certain models of that central transformer being a fire hazard.

Later model (mid 1970s) Princess and Trimline sets used LEDs to illuminate the dial. These were powered from the telephone line and needed no transformer.

I don't know if rotary dial telephone sets will operate on modern VOIP-based lines. (In one sense, my guess is that they should because 'flashing' (sending a 1/2 second pulse for Call-Waiting or 3-way-calling) is still a standard signal, and the base station would have to accept such signals.) Rotary sets will not operate on ISDN or digital lines, but these lines require special sets.

*Back in the 1950s some 500 sets had a little mushroom dial lamp atop the dial. ***** Moderator's Note *****

Does anyone make phone sets that will connect directly to a two-wire ISDN line? All the ones I know about have "T" (i.e., four wire) interfaces, and so require an adapter.

Bill Horne Moderator

I was a tech at New England Telephone, and we used shielded twisted pair for T1 lines on the frame. I remember that it was a PITA to ground the shields sometimes: we had to solder pieces of wire to the shield-ends and tie them down under a mounting screw. I don't know why, but some of the T1 repeater blocks had no ground lugs on them.

For some reason, the techs used to use the same cable - shielded twisted pair - to connect fault locate circuits and order wires. I dug out the "T" diagram and showed the foreman that it called for regular cross-connects, but to get him to believe me, I had to claim that the third-liner in Engineering had told me about it.

Bill

I think you'd have a much harder time finding somebody who made ISDN phones rather than worrying about if they are U interface or S-T interface. If you really are going that hardcore retro, mounting an NT-1 on the backerboard to support your 2-pair S-T ISDN phone probably isn't much an issue.

I think the AT&T/Avaya ISDN phone I have is S-T, but the documentation (available at does mention that their 6500 series has a U-Interface option when buying.

You can drive pretty far on the S-T bus, long enough for a residential application, although in practice, ISDN phone wasn't exactly without constant hiccups. Could just be the one I have though too.

And at MRC of $78 + CALC in these parts for a BRI (if you could actually find a sales rep that knew what the H you were talking about) isn't really worthwhile either.

I think they still sell enough to radio stations for remotes that it won't be going away any time soon.

I have some customers who still need ISDN, because they have work-at-home setups and don't want their cow-orkers to know when they aren't in the company building.

ISDN provides exceptional voice quality: so good, in fact, that it's a major asset to managers who choose to avoid the questions which come with being "out of the office" more than others. Since almost all of my customers whom are in that situation work in buildings that have ISDN sets on a PBX, it's easier for them to use a familiar instrument at home, but it's always been the kind that requires a "T" interface, and I'm looking for alternatives.

At least in Massachusetts, ISDN lines can be ordered for residential service, and they cost little more than POTS when installed in a home. Data calls are always billed by the minute, but voice is flat-rate, so it's a minor expense when used only for voice calls.

Bill