Rega IT Replacement Laptop AC Power Adapter/Charger for COMPAQ PRESARIO CQ40-123AU CQ40-123AX CQ40-123TU CQ40-124AU laptop enables you to operate your notebook or charge the Adapter from electrical power outlets. If you are running your computer on AC power with a Adapter installed, the adapter charges the Adapter (if needed) and maintains its charge. When the system is off, the AC adapter will charge the Adapter and then maintain its charge. Made from highest quality parts each Rega IT replacement adapter confirms to specifications similar and guaranteed to meet or exceed your laptop's minimum requirements. Each adapter also passes necessary authentication certifications like CE, ROHS etc. Before leaving the factory, so you can be rest assured for its quality, durability and performance. Please make sure that you are selecting the correct adapter as per you old charger specification. Please compare your old Adapter Power Rating i.e. Volts (V), Amps (A), Watt (W) and Pin / Tip / Connector Size.