Abstract: A flexible multi-processor communications system supports variable message lengths and variable groups and application designations at respective processors. The receiving processors determine what action, if any, needs to be taken in response to the combination of group and application information in the messages. The receiving processors can include pluralities of pre-stored groups and applications along with associated priorities and the functions to perform.

Abstract: An audible output device, of a type usable in a fire alarm system, incorporates a multi-frequency waveform generator. The generator produces a plurality of frequencies with predetermined duty factors during various time intervals on a repetitive basis. The multi-frequency drive signal is in turn coupled to an audible output device such as a piezoelectric horn or the like. The multi-frequency audio output provides an indicator to persons adjacent to the device of the presence of an alarm condition.

Abstract: A flexible multi-processor communications system supports variable message lengths and variable groups and application designations at respective processors. The receiving processors determine what action, if any, needs to be taken in response to the combination of group and application information in the messages. The receiving processors can include pluralities of pre-stored groups and applications along with associated priorities and the functions to perform.

Abstract: A flexible multi-processor communications system supports variable message lengths and variable groups and application designations at respective processors. The receiving processors determine what action, if any, needs to be taken in response to the combination of group and application information in the messages. The receiving processors can include pluralities of pre-stored groups and applications along with associated priorities and the functions to perform.

Abstract: A supervisable multi-processor communication system includes circuitry and executable instructions for evaluating the communication capability of a plurality of branches in the system. Branches which exhibit a non-communicating condition, such as an open circuit can be identified. By conducting communications with electrical units on identified branches, the location of an open circuit, relative to one of the electrical units can be established.

Abstract: A flexible multi-processor communications system supports variable message lengths and variable groups and application designations at respective processors. The receiving processors determine what action, if any, needs to be taken in response to the combination of group and application information in the messages. The receiving processors can include pluralities of pre-stored groups and applications along with associated priorities and the functions to perform.

Abstract: A communication protocol facilitates transmission at maximum rates for various types of cables. Signal to noise characteristics are improved by using voltage waveforms. The protocol can be used to transmit information between a common control unit and a plurality of spaced apart devices coupled thereto. Alternately, the protocol can be used for transmission of information between devices. The common control unit transmits clock pulses, while in a low impedance state. The devices respond to the clock pulses and transmit data on the communications link, in a low impedance state, when the common control unit has assumed a high impedance state. Clock signals and data signals are separated to improve signal to noise characteristics by transmitting same with opposite polarities. A clock detection circuit responds to the polarity of the clock pulses. A data detection circuit responds to the polarity of the data pulses.

Abstract: A communication protocol facilitates transmission at maximum rates for various types of cables. Signal to noise characteristics are improved by using voltage waveforms. The protocol can be used to transmit information between a common control unit and a plurality of spaced apart devices coupled thereto. Alternately, the protocol can be used for transmission of information between devices. The common control unit transmits clock pulses, while in a low impedance state. The devices respond to the clock pulses and transmit data on the communications link, in a low impedance state, when the common control unit has assumed a high impedance state. Clock signals and data signals are separated to improve signal to noise characteristics by transmitting same with opposite polarities. A clock detection circuit responds to the polarity of the clock pulses. A data detection circuit responds to the polarity of the data pulses.

Abstract: A multi-unit ambient condition detecting system incorporates either a wired or a wireless communication medium wherein the units are in bi-directional communication with one another. Units can incorporate programmed processors and ambient condition sensors such as smoke or gas sensors. In response to detected local ambient conditions, the respective units can transmit messages indicative of the level of sensed ambient condition to other units in the system. The units can maintain running totals of levels of ambient conditions received from other units in the system and combine those received indicators, along with one or more locally generated indicators, to determine that a selected condition, such as fire or gas is present in at least a portion of the region being monitors. Output devices coupled to the communication medium can provide human discernable audible or visible indicators of the presence of one or more selected conditions.

Abstract: A system and method to detect ground faults in a multi-processor communication system that includes a communications link that extends between the processors. The processors isolate different sections of the link. Measurements made with different isolated sections establish the location of the fault. The processors can also make measurements of the link to establish the magnitude of a shunt impedance on the link. Where an abnormal value of shunt impedance is detected, the respective devices can activate or deactivate solid state isolation circuitry to disconnect a section of the link exhibiting the abnormal level of shunt impedance.

Abstract: A multi-processor communication system includes a plurality of processors in bidirectional communication with one another. One processor can transmit a message to an intended recipient. The message can be correctly received by other processors. In the event that the intended processor does not correctly receive the message and transmits a failure indicating message, the other processors, upon detection of the failure will retransmit the message. Ambient condition sensors can be coupled to some of the processors.

Abstract: A self-monitoring power supply can be incorporated into electrical devices which are part of a multi-device communication system. The power supply is energized by electrical energy received from a medium on an intermittent basis. The self-monitoring circuitry assures that the device has sufficient energy for carrying out its functions. Noise rejection and noise immunity can be enhanced in such devices by circuitry which upon detection of a transmission start signal or a clock pulse locks out data signals for a predetermined period of time and upon detection of a data signal locks out transmission start or clock pulses for a predetermined period of time.

Abstract: A point level sensor senses capacitance of a material in a vessel to determine level. The capacitance is input to a comparator which is part of an oscillator circuit developing a square wave signal having a period corresponding to capacitance. A microprocessor includes an internal counter which determines the period of four pulses to determine an average period. The microprocessor drives relay circuits providing discrete outputs according to specific precalibrated levels to be sensed. The point sensor includes a self-test mode which operates once per second to test for shorting of the probe, expected frequency response and an open probe.

Abstract: A protection device for a waterbed protects the water bladder and water heater from damage due to overheating when a dangerous condition, such as an insufficient level of water within the bladder or an element of the waterbed surroundings interposed between the bladder and the water heater, arises. The protection device employs a detector in the form of two capacitance plates placed adjacent to the water bladder and connected to a circuit which is operative to prevent power from being supplied to the water heater upon detection of a dangerous condition. The capacitance of the detector plates varies with the level of the water within the bladder and with the presence of a surrounding element between the bladder and heater.

Abstract: A photoelectric combustion products detector for periodically sampling the ambient air includes a sampling circuit capacitively coupled to an AC source, so that the coupling capacitor produces at the sampling circuit a source current 90.degree. out of phase with the AC source voltage, which is rectified to provide a supply voltage. Sampling is controlled by a NAND gate having at its inputs a varying threshold level which is proportional to and in phase with the supply voltage. A ramp signal generator connected to one gate input terminal enables the gate when the ramp signal exceeds the varying threshold level. The other input terminal of the gate is connected to a timing circuit comprising a Zener diode, a capacitor and a discharge resistor which produces a short trigger pulse at or near each positive zero crossing of the AC source voltage, the coincidence of a trigger pulse with an enabling period causing the gate to actuate the sampling circuit.

Abstract: An appliance control system includes a central control unit and a plurality of slave units each including a user-programmable microprocessor and respectively plugged into outlet sockets of a power main in a building, appliances being respectively coupled to the slave units. The system permits manual or automatic transmission of command signals and status request signals from the central control unit to individually addressed slave units, and transmission of status signals from the slave units to the central control unit. Certain slave units include lamp dimmers which can be operated either remotely from the central control unit or locally at the slave unit, the microprocessors of these slave units being programmable to remember a predetermined brightness level, so that the lamp can be remotely turned on to that predetermined level. Means are provided for turning the appliance off at the remote appliance site while maintaining the appliance under the control of the central control unit.