The present invention is generally related to radiotelephones, and more particularly to a cellular portable telephone which accommodates a power source change and corresponding operating mode change during a radiotelephone call.
Cellular portable telephones currently have batteries with capacity for one-half hour of continuous operation. As a result most users typically carry one or more spare batteries so that they can switch to another battery when the portable telephone indicates that the battery voltage is low. However, when the battery is removed during a cellular telephone call, the call is terminated and the user must redial the call. Interruption of the power source and termination of a cellular telephone call in process also occurs when the user plugs the cellular portable telephone into a vehicle's battery by way of a vehicular adaptor installed therein, such as a battery eliminator connected to the vehicle's cigarette lighter. For the foregoing reasons, there is a need for a cellular portable telephone which accommodates a power source change and corresponding operating mode change during a cellular telephone call.