Uniden DECT1725 - Manual (Page 42)

How many telephones can I have?
All items of telephone equipment have a Ringer
Equivalence Number (REN), which is used to
calculate the number of items which may be
connected to any one telephone line.
The total recommended REN on one line is 3.
If you exceed a REN of 3, your phones may not
ring. With different telephone types there is no
guarantee of ringing, even when the REN is less
than 3. Your phone has a REN of < 0.01 (even with
additional handsets and chargers registered to
your base).
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