REN Numbers

Not sure exactly which forum to post in, so please move if you don't agree. There is a FTTC service on the line and I think an answer reflecting modern lines and equipment, and any adjustments that could make to previously issued advice, would be useful to others.

I would like to know if REN numbers are still a necessary consideration on a BT line.

I have today purchased a new telephone, and moved the old one (with real bells, needed the ring wire connected) onto a spare extension socket, so now the setup is like this:

Master socket with FTTC faceplate: 1 telephone with electronic ringer (REN=1) plus data extension to FTTC modem / BT Home Hub 3 (Does this have a REN value?)

Extension 1: 1 telephone with electronic ringer (REN=1)
Extension 2: 1 telephone with real bell ringer (REN=1)
Extension 3: 1 DECT cordless telephone (REN=1)
Extension 4: 1 telephone with electronic ringer (REN=1; although very difficult to read the sticker!)

Will this number of devices on the line cause problems (I recall a limit of 4.0 previously)?. All 'phones do appear to ring and work fine.

Even if this would be above the theoretical maximum, how can I tell if there is a problem; what will happen and is this a definite thing to avoid?

Thanks,
David

Should be no problem. The way to really go is to add more DECT handsets rather than wired phones.

So long as everything is filtered properly and not some horrible star wiring setup with each phone having its own filter.

All extensions are wired off the removable lower "front third" of the master socket, which I understand to be the filtered part of the socket. The data extension was installed by the BT engineer, and is connected to the two terminals middle left when the lower front third is removed.

All extensions are wired in series from the four terminals on the front third of the master socket, such that the intermediate sockets have two cables feeding them, and the last extension has just one. All ADSL plug in filters were removed when the FTTC service was installed.

David

Should be fine

I understand lots of devices really should have a REN of 0.1 or 0.2, but they never quote fractions so say they are all 1. It was really an issue in the dim and distant past with real bells using real current; pretty much irrelevant now.

BT will only guarantee to provide ring current for a maximum REN of 4 - although in practice it tends to be a little higher given that most lines are not 10 km long and the loop resistance does not affect the line enough to bring the limit into play.

Any device with an electronic ringer and power supply, such as a DECT cordless will have a REN of way less than 1 and whereas it was common practice to label devices with a REN of 0.5 it seems to have fallen out of use and they default to 1. Even a standard electronic ringer is less than 1. So, everything should be fine.

If a problem develops you might hear a very short ring at the start and then some "tinkling" from te electronic ringers. If it does happen, try unplugging one or two 'phones and calling the number to see what happens.