Abstract: An option attach connector has a first indicator bit combination that alerts the device that a public switched telephone network connection has been made to it. The presence of the first indicator bit combination is a signal to the device that telephone, FAX, and E-MAIL communications applications are to be conducted over a PSTN link. The presence of the first indicator bit combination invokes a stored computer program to provide appropriate connections between the PSTN link and the telephone, FAX, and modem hardware in the device. The connections are made by an audio multiplexer that receives control signals from the system CPU, while executing the stored computer program. The program determines the communications application selected by the user and selectively configures the PSTN link to be connected to the either the ear piece and microphone for voice communications, or to the FAX/modem for FAX communications, or to the modem alone for E-MAIL communications.

Abstract: A battery operated computer includes a battery having a plurality of serially connected banks of battery cells that are monitored during operation of the computer to detect a nearly depleted battery bank and a fully depleted battery bank. The computer also includes a plurality of microprocessors including a host or system processor, a service processor and a power subsystem processor. When a nearly depleted battery bank is detected, the power subsystem processor is interrupted and it sends a message to the service processor which in turn interrupts the host processor. An interrupt handler then powers down the system. When a fully depleted battery bank is detected, the battery is immediately disconnected and the system is shutoff to prevent polarity or cell reversal.