Low cost power back-up system for cordless telephone system

A method for powering a base unit of an electronic apparatus comprising:

• detecting by the base unit that a power outage condition has occurred;
• placing a portable unit of the electronic apparatus into a cradle of the base unit;
• receiving power by the base unit from a battery pack of the portable unit;
• preventing power from flowing from a power supply of the base unit to the portable unit during the time when the power outage condition occurs, and
• supplying the power from the power supply of the base unit to the portable unit when detecting that the power outage condition is no longer occurred.

A cordless telephone system for continued operation of a base unit during a power outage condition, the system comprising:

• a first cordless telephone portable unit, including a rechargeable battery pack, and charge terminals that are electrically coupled to the rechargeable battery pack;
• a base unit capable of communicating with the first cordless portable unit to place and receive telephone calls, the base unit comprising:
• a cradle that is configured to receive the first cordless portable unit, the cradle comprising electrical contacts for electrical coupling with the portable unit charge terminals when the portable unit is disposed within the cradle;
• a power supply for receiving electrical power from an external power source;
• a line status control circuit coupled to the base unit power supply which outputs a signal indicative of whether the voltage present on the power line exceeds a predefined level;
• a portable unit charging circuit responsive to an output of the line status control circuit to provide electrical energy to the electrical contacts when the voltage present on the power line exceeds a predefined level;
• a power control circuit responsive to an output of the line status control circuit to couple the electrical contacts to an input of a voltage regulator circuit when the voltage present on the power line falls below a predefined level;
• and
• means for preventing power from flowing from the power supply of the base unit to the portable unit that is disposed within the cradle when the voltage level of the power supply of the base unit is lower than the predetermined level, and for allowing the power flowing from the power supply of the base unit to the portable unit when the voltage level of the power supply of the base unit is higher than the predetermined level,
• wherein the base unit operates using power supplied by the first portable unit rechargeable battery pack when the external source of power to the power line fails.