Plantronics CALISTO HEADSET WITH BLUETOOTH USB ADAPTER 56-K61A-15000 - Manual (Page 9)

5
Charging Your Headset
Before using, you must first charge your headset. The indicator light
glows solid red while charging and turns solid blue when the headset is
fully charged.
Charge the headset for a minimum of 2 hours. Battery talk time is up to
8 hours.
NOTE Do not use headset while chargng and do not connect the charger
while headset is in use.