Compaq 1610 Reference Manual page 121

The Ringer Equivalence Number (REN) assigned to each
terminal device provides an indication of the maximum number
of terminals 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
Ringer Equivalence Numbers of all the devices does not exceed 5.
The Ringer Equivalence Number (REN) for this device is 0.8.
For the location of the authorized Canadian maintenance facility
nearest you, call 1-800-263-5868 or contact:
Compaq Canada, Inc.
45 Vogell Road
Richmond Hill, Ontario LA5B 3P6