Binatone iDECT L1i System User Manual page 6

Connection and conditions for use:
You can connect your iDECT system to a direct exchange line (DEL) on a
local exchange with its own phone number; to an extension socket
connected to a DEL; or to an extension on an approved compatible PBX.
Do not connect as an extension to a payphone.
The ringer equivalence numbers (REN) of all equipment (phones, fax
machines, modems, etc.) connected to an exchange line must not
add up to more than 4, otherwise one or more of them may not
ring and/or answer calls correctly. The iDECT system has a REN of 1, and
most other telephones have a REN of 1 unless marked otherwise.
To use your handset and base together, you must be able to establish a
radio link between them. The signal between the handset and base is in
accordance with the normal standards for a DECT phone: Maximum range
up to 300 metres outdoors or 50 metres indoors.
The signal range may decrease if there is any large metal object between
the handset and the base, such as a refrigerator, a mirror, a filing cabinet,
metallic doors, or reinforced concrete. The signal strength may also be
reduced by other solid structures like walls, or by other radio or electrical
interference.
2