ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Telephone Systems

Yes -- Most certainly!

The ringing voltage can give quite a tingle if you happen to be across the line when someone calls. I always try to busy out a line when working on it if I can (leave a connected phone off-hook or just jumper the loop with a clip lead).

Ringer voltage is around...90 volts or so?

It can sting you a bit....especially if your hands get sweaty while working. But it's not going to throw you across the room.

When I was adding extensions to my mom's phone I disconnected the wires at the main entry terminal block before the junction box I put in (I wired the thing up in a "star" configuration - one pair of wires to each extension box).

Well, Paul, if an Electric hazard can arise, why is there no requirement to have some form of Isolator,when working on these
circuits?, you can't simply tell the homeowner, to make sure no-one rings up, while you are working on their phone circuits.
What gives?.

Sven,
Yes, usually around 90V by the time it reaches the house, although on a lightly loaded line very close to the CO it could be higher. As you said, it's not going to throw you across the room, but the ringer voltage can pose much more of a threat to a lineman working in a water-logged telephone manhole.

Trumpy,
Subscribers (sorry, "customers" as BT calls us nowadays!) have been allowed to install their own extension wiring here since the 1980s.

The latest master jacks (i.e. the jack at which the incoming TelCo line terminates) incorporate a pull-out panel to which extension wiring can be terminated.


The lower section of this jack pulls out and disconnects the extension wiring from the line.

You can't see it in the picture, but the panel actually connects the the fixed portion using the same style jack. Thus when the panel is removed for work it's possible to leave a phone connected directly to the incoming line. (And of course, the TelCo tells people to remove the panel and plug straight into the line if they're having any problems in order to determine if the fault is on the internal extension wiring.)

I can't speak for many other countries, but many (newer) installations in the U.S. incorporate a "network interface." In many instances it's just a split duplex phone jack, line on one side, wiring to jacks on the other, linked by a short patch cord.

AFAIK in Austria any fixed wiring belongs to the phone company and is not to be touched by the customer. Earlier phone connector boxes (for our typical hardwired phones) had a sealing sticker over the cover screw. Extensions were only possible with single lines, and hence rather rare. (a vast majority of households, especially in the cities had party lines with in rural areas up to 10 subscribers on one line, in cities up to 4, thus the name "quarter lines", with a rather complex relais system preventing eavesdropping by the other subscribers).

FWIW, in Canada, the government agency overseeing the telephone industry, in early 1998 or so "Gave" all inside wiring, and the
whole responibility for, to the customer, although fo years you could buy your own extension line wiring goods for years and could do the work yourself.

Back when our phones were all under the GPO (General Post Office), internal wiring was installed by the GPO and nobody else was supposed to interfere with it in any way.

They didn't go to the lengths of putting seals on the junction box covers, though.

Today, the incoming line and the master jack (pictured above) still belong to the TelCo (BT in most areas). The subscriber can remove the plate I mentioned above to connect extension wiring, but is not supposed to open the master jack any further.


[This message has been edited by pauluk (edited 11-29-2002).]

As far as I am aware, Paul, no-one ever touched Phone wiring when it was under the control of the old P&T, but once this was sold off, the floodgates opened, every person was putting in extra telephones in their houses, using any sort of wire that they felt like(NB:This was under the old 3-wire system).
Now, people like myself over here, are trying to bring these "hook-ups", into compliance, with the new Telecom NZ requirements, are finding all sorts of wire.
We are now using a 2-wire system, which means that all of the sockets on the line are Masters, there are no Secondaries, in these systems.

Every single piece of equipment here was sealed. 1950ies and earlier even had pressed lead seals on it! In the 60ies they changed to orange stickers with the post office logo on them. They were used until about 1995, or maybe even until the privatization to Telekom Austria in 1998.

I guess I should have mentioned an exception. When the GPO monopoly on telephone service ended and BT allowed individuals to carry out their own wiring, it was under the instructions that this could only be done where BT had already installed the new-style jack. People weren't supposed to tamper with the old style 1/4-inch jacks or hard-wired units.

One good reason for this was that at that time there were still quite a lot of party lines in use. Inadvertant reversal of connections could have resulted in outgoing calls being charged to the other party!