Brother FAX 1840C - Manual (Page 230)

EQUIPMENT ATTACHMENT LIMITATIONS
(Canada only)
NOTICE
This product meets the applicable Industry Canada technical
specifications.
NOTICE
The Ringer Equivalence Number is an indication of the maximum
number of devices allowed to be connected to a telephone interface.
The termination on an interface may consist of any combination of
devices subject only to the requirement that the sum of the RENs of
all the devices does not exceed five.