Abstract: A communication system comprising a wireless keyboard for emitting infra-red signals, a receiving unit for converting the infra-red signals to an electrical signal, a tuning and amplifying circuit coupled to the receiving unit for tuning and amplifying the electrical signals, a carrier filtering circuit for removing the carrier component of the input signal, a single-shot circuit coupled to the carrier filtering circuit for converting its input signal to a known code wave form, and a microprocessor for receiving the code wave. The invention allows multiple users to operate their wireless keyboards without interference.

Abstract: In a battery powered data processing system having an oscillator and a microprocessor connected to the oscillator, the microprocessor has a programmable standby mode and circuit responsive to the standby mode for disabling the oscillator. The system uses a sensor circuit to generate a reset signal to reset the microprocessor from the power down mode when a key is depressed. A signal generator is responsive to signals from the oscillator for disabling the reset signal.

Abstract: A computer keyboard interface is disclosed with an improved system for controlling the signals on a clock line and a data line for communication between the keyboard interface and the system interface. Two bi-directional input/output ports are used, one for the clock line and one for the data line. The data and clock lines are then used not only for the transmission of data but also used by the keyboard interface for sensing status signals from the system interface. This simplifies the keyboard interface design.