You can use the Cisco Wireless IP Phone 8821 Desktop Charger to charge your Cisco Wireless IP Phone 8821 and spare phone battery. The charger works on AC power or from a charged spare phone battery. It can be secured with a standard laptop cable lock. This charger has a label on the back to show the maximum voltage (4.35 V).&lt;br /&gt;&lt;br /&gt;You can use the Cisco Wireless IP Phone 8821-EX Desktop Charger to charge your Cisco Wireless IP Phone 8821-EX and spare phone battery. The charger works on AC power or from a charged spare phone battery. It can be secured with a standard laptop cable lock. The charger looks the same as the Cisco Wireless IP Phone 8821 Desktop Charger except that it shows the graphic of the Cisco Wireless IP Phone 8821-EX and doesn&#39;t have the voltage label.