Battery charging
Once you have installed the battery, the screen indicates the battery status (see the table below). For best performance, keep the handset in the telephone base when not in use. The battery is fully charged after 13 hours of continuous charging.
Battery indicators | Battery status | Action | ||||||||
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The screen is blank, or | The battery has no or very | Charge without interruption | ||||||||
displays Place in charger | little charge. The handset | (at least 30 minutes). | ||||||||
and |
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The screen displays | The battery has enough | Charge without interruption | ||||||||
Low battery and |
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The screen displays | The battery is charged. | To keep the battery charged, | ||||||||
HANDSET X. |
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| or charger when not in use. |
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• If you place the handset in the telephone base or charger without plugging in the 
battery, the screen displays No battery.
Add and register a handset
You can add new handsets (purchased separately) to your telephone system. Each handset must be registered with the telephone base before use. Additional handsets registered to the telephone system are assigned numbers in the sequential order.
When first purchased and properly charged, each expansion handset displays Put handset on BASE to register. The new handset should be charged without interruption for at least 30 minutes before registering it to the telephone base.
To register a handset:
. Make sure the handset is out of the telephone base or handset charger and shows Put handset on BASE to register. Place the handset you wish to register in the telephone base.
IS7121 base | Do not place the handset |
| in the charger. |
. The handset displays Registering handset... then displays HANDSET X Registered, and you hear a confirmation tone from the handset when registration completes. It takes about 60 seconds to complete the registration process.
Deregister handsets and doorbells
If you want to replace a handset, or reassign the designated handset number of a registered handset, you must deregister all system devices and then register each handset/doorbell individually.
Make sure you plug in AC power for the doorbells before deregistration.
To deregister all handsets and doorbells:
. Press and hold 
/FIND HANDSET on the telephone base for about 10 seconds until the IN USE light flashes.
. Immediately press 
/FIND HANDSET again. You must press
/FIND HANDSET while the IN USE light is still flashing. The IN USE light flashes for about five seconds.
3.All handsets show Put handset on BASE to register and all doorbell lights flash quickly. The deregistration process takes about 10 seconds
to complete.
To register the handset(s) to the telephone base again, follow the registration instructions above.
