AT&T TL90078 - Manual (Page 12)

Getting started
Adding and registering handsets
Before using a new TL90078 handset, you must register it
with the AT&T TL92278/TL92328/TL92378 telephone system
(purchased separately). The AT&T TL92278/TL92328/TL92378
telephone system can accommodate up to 12 handsets.
The handsets provided with the TL92278 come pre-registered
as
HANDSET 1 and HANDSET 2. You can register up to 10
additional handsets to the telephone base, and they will be
assigned numbers in the order they are registered (
HANDSET 3,
HANDSET 4, HANDSET 5 and so on).
The handsets provided with the TL92328/TL92378 come pre-
registered as
HANDSET 1, HANDSET 2 and HANDSET 3. You
can register up to nine additional handsets to the telephone
base, and they will be assigned numbers in the order they are
registered (
HANDSET 4, HANDSET 5, HANDSET 6 and so on).
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