Ringer Equivalence Number (REN)

Ringer Equivalence Number (REN)

All items of telephone equipment have a Ringer Equivalence Number (REN) which is used to calculate the number of items that may be connected to any one telephone line. Although you may have any number of telephone sockets, it is important to limit the number of telephones and other items including faxes, answer machines and modems, connected to your telephone sockets. Every telephone or item connected to the telephone has a REN, usually displayed on the base of the device (near to the green approval sticker) or in the user manual for the device. Most telephones have a REN of 1, but some faxes and modems may have a REN of more than 1.

Simply add up the REN numbers of all the devices connected to your phone line anywhere in the house, the total should not exceed 4. You are likely to have technical problems (with equipment not working or ringing very quietly) if you exceed the REN limit of 4. If some or all of your phones fail to ring or some ring very weakly then try unplugging devices one at a time until they work.

The REN of a telephone line can be increased by purchasing what is known as a REN extender, most will take you up to a REN of 8. They tend to cost around 40 pounds.

All advice is either supported by references (cited in the text) or is based upon peer reviewed professional opinion. Our advice is impartial and not influenced by sponsors or product suppliers listed on the site.
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