The adapter only supplies DC power, so a charging circuit internal to the transmitter regulates the battery charging profile and automatic cutoff to prevent overcharging.
When the adapter is first plugged in, the green LED charge status light will blink for a few seconds (or longer depending on the state of charge) and then turn steady green to indicate fast charging is initiated.
Depending on the batteries state of charge, charging may take up to 2 ½ hours for the 6-cell NiMH 800mAh capacity battery (6 hours for the 6-cell NiMH 2000mAh). Upon fast charge completion, the green LED will turn off and the charger circuit switches to pulsed trickle charging. Pulse trickle charging simply maintains the full charge level indefinitely without any risk of overcharging.