Abstract: Apparatus for a monitoring and signalling system such as a home health care system includes a plurality of sensors operative to monitor the occurrence of activities performed by an individual in his or her residence and to produce binary coded signals indicative of the occurrence of the monitored activities. Each signal comprises six successive identical messages within a one-second interval, with each message including a binary word identifying the monitoring and signalling system, the particular sensor originating the signal, and the nature of the monitored activity. Each message further includes a preamble and a pair of interwords on opposite sides of the binary word.The apparatus in accordance with the invention includes a microprocessor which operates to repetitively sample each signal originating with a sensor to determine the binary content of the signal and to extract a binary word from a message while rejecting preambles, interwords and "glitches" (noise) present in the signal.

Abstract: Electrical power supply for use with apparatus which transmits a predetermined message. When an input signal is received, a source of electrical energy is connected to a power output terminal by turning a switching transistor on. A latching circuit holds the transistor on after termination of the input signal. Elements of the apparatus which are connected to the power output terminal to obtain operating power transmit the predetermined message when the electrical energy is supplied to the terminal. When the transmission is complete, the apparatus produces a termination signal to the latching circuit causing it to turn the switching transistor off and thus disconnect the source of electrical energy from the power output terminal.

Abstract: A logic level converter converts an input signal having first and second voltage levels to an output signal having first and third voltage levels in which the voltage excursion of the output signal is greater than that of the input signal. The converter comprises first and second cross-coupled inverters in which the second inverter provides the output signal and is biased with respect to the first and third voltage levels and in which the first inverter is biased with respect to the third voltage level and the digital input signal. A voltage divider is associated with the first inverter to insure sufficient voltage swing for proper switching of the inverters. The inverters have dissimilar gains to insure that when the inverters are biased at equal voltages, the inverters always assume a predetermined state. The converter is implemented with PMOS field effect transistors and includes capacitors for increasing switching speed.