Abstract: A data storage system comprised of a disk drive including a magnetic disk for storing an operating system program, a dynamic RAM memory circuit for temporarily storing the operating system program, a static memory circuit for temporarily storing customer entered data, and a direct memory access controller for periodically transferring the customer entered data from the static memory circuit to the magnetic disk and for transferring the operating system program from the magnetic disk to the dynamic RAM memory circuit in response to execution of a bootstrap or power-up program by the microprocessor. In the case of a power down during entry of customer entered data, the customer entered data is saved in the static memory and is transferred to the magnetic disk during the subsequent power up thereby avoiding the use of possibly corrupted data on the disk drive.

Abstract: A communication switching system for routing digital voice and data signals and message signals between a plurality of peripheral circuits disposed in one or more peripheral subsystems and a main controller. Each peripheral subsystem is comprised of a peripheral switch matrix controlled by a peripheral control processor for switching the voice and data signals between predetermined peripheral circuits and the circuit switch matrix. The voice, data and message signals are transmitted through a circuit switch matrix of the main controller on predetermined time slot channels. The message signals are transmitted via communication controllers associated with the main controller and each of the peripheral subsystems according to a bit oriented data link protocol. The message signals are transmitted asynchronously during a predetermined one or more dynamically allocated time slot channels of the circuit switch matrix. The data link protocol guarantees error-free transmission of a plurality of message signals.