Abstract: A battery-operable portable electronic device, having a removable main power source and an auxiliary power source, generates a power failure interrupt signal when it detects a power failure of the removable main power source. Upon detection of the power failure, the electronic device enters a power down mode in which it monitors recovery from the power failure. The electronic device monitors recovery from the power failure by using a battery check routine it pushes on the stack of a microcontroller, and pops off the battery check routine from the stack upon determining a stable recovery, while returning to an exact point in a main program it left when it detected the power failure, the exact point in the main program being represented by a program counter value automatically pushed on the stack upon occurance of the power failure interrupt signal.

Abstract: A radio pager device includes a display having a zoomed-out multiline mode and a zoomed-in single line mode for display of at least a portion of a series of characters at a time extracted from a message having an address or identification code which is among those from which the pager is authorized to extract message data. The zoom mode is selectable on either a system basis, by default, or a message basis. The message specific zoom mode is determined by accessing display per address information stored in volatile memory and programmable by the user. In the single line mode, continuous horizontal character by character scrolling may be selected by the user and controlled by key actuation to toggle between a stationary paused state and a continuously scrolling state.