Abstract: A modular alarm system includes a plurality of sensing devices, each of which is adapted to sense the presence or absence of a particular condition, specifically a fire or over heat condition (hereinafter referred to merely as a fire condition), and the presence or absence of a fault including a short circuit or open circuit. The system also includes a detector module for producing an equal plurality of identical logic output signals indicative of and in response to the presence of the particular condition being monitored at the various sensing devices and a single, identical logic output signal indicative of and in response to the presence of a fault at any of the sensing devices.

Abstract: A brake pad wear detection system comprises a brake having a brake pad and a conductive braking face, the brake pad and the conductive braking face engaging during braking. A sensor loop is embedded in the brake pad and positioned to be broken when the wear to the brake pad exceeds the working limit. An indicator means and a detecting means for operating the indicator means are provided, the detecting means detecting contact between the sensor loop and the braking face as well as breakage of the sensor loop.

Abstract: A time multiplexed sensor monitoring system. A plurality of remote sensor units are connected to a central control unit by a two-wire bus line. Power is supplied to the remote unit sensors by the central control unit. Synchronization of the remote units is provided through momentary interruptions in the power supplied to the remote sensor units. The use of a single two-wire bus line for both application of DC signals to the respective remote sensor units and communication of data from the remote sensor units to the central control unit is facilitated by use of double tone multi-frequency (DTMF) signalling techniques.

Abstract: A printed circuit board loaded with an electronic circuit and constructed to be capable of being inserted in and withdrawn from a bus line on on-line status, in which the input to or the output from the printed circuit board is locked out in response to the presence of two conditions, one is the presence of a demand for insertion or withdrawal of the printed circuit board on on-line status and the other is the presence of such a condition that no information exchange is being made between the printed circuit board and other unit connected with the bus line, thereby releasing the electrical connection between the bus line and the printed circuit board so that the printed circuit board can now be inserted in or withdrawn from the bus line on on-line status.

Abstract: A process control installation has means for sensing a plurality of physical conditions connected to means for comparing the condition to a reference. A differential signal is fed to a corresponding reproduction circuit which in turn feeds it to inputs of a plurality of majority decision circuits. The majority decision circuits are in turn connected to pairs of logic circuit trains which in turn are connected to other logic circuitry for intrinsic security.

Abstract: A circuit for distinguishing between two classes of alarms on a single loop. An alarm of a first class causes an impedance of a first predetermined value to be added in the loop; and an alarm of a second class causes a much larger additional impedance, or an open condition, to be inserted in the loop. The loop is bridged across an element of a voltage divider and, therefore, the loop characteristics, including the changed characteristics due to the impedance change in response to an alarm of either class, controls the potential of a test point of the voltage divider. Voltage comparators monitor the potential of the test point relative to control potentials, and cause relays to provide a no alarm signal, a first alarm signal, or a second alarm signal when there is no alarm condition on the loop, an alarm of the first class, or an alarm of the second class, respectively, on the loop.

Abstract: An alarm system for indicating excessive leakage of liquid across the engaging seal faces of a mechanical seal, especially those seals which are so positioned to prevent visual inspection.

Abstract: A tire height warning system for use on vehicles employing pneumatic tires. The system includes a tire height sensor, mounted inside the inflation chamber of each monitored wheel of a vehicle, to detect low inflation or overload and responsively transmit an RF signal to a remote receiver for informing the vehicle operator of a potential tire failure. The tire height sensor is a unitary structure including an inflation value, a height probe and a self-powered RF transmitter compressibly mounted within a wheel adapted with a retaining clip.

Abstract: A device for monitoring and indicating the operational readiness of a gas-measuring instrument fitted with a built-in chargeable battery has visible luminescent diodes that emit different colors when energized and which are disposed in an electrical flip-flop circuit with rheostats for adjusting the switchover values of the circuit which is provided with a pair of input leads for connecting a chargeable battery to the circuit.

Abstract: An alarm device and system which is adaptable to a variety of uses and conditions for protecting homes, equipment, buildings and the like by alerting or informing distant or nearby personnel to changes of conditions from within predetermined limits.

Abstract: A bed mat having a sensor for detecting abnormally high temperatures and for detecting when the occupant of the bed is not in it is connected to a control console which has circuits for producing a first electrical signal having a first characteristic in response to the detection of an abnormally high bed temperature and a second signal having a second characteristic in response to the detection of the absence of the bed occupant. In one form of the invention, these signals are applied to the conventional nurse call system to produce sensory signals at the nurses' station, for example, indicative of the detection of high temperature or absence in a way such that they can each be distinguished from the the signal produced at the nurse's station by the use of the nurse call button by the patient. Provision is also made for coupling of a smoke detector into the system for actuating the high temperature alarm signaller if smoke is detected.

Abstract: A warning apparatus to indicate to a driver that the headlights of the vehicle have been left on after the ignition has been turned off includes a timer circuit which is operably connected to the ignition switch, the headlight switch, and the horn of the vehicle. The timer circuit energizes the horn for a predetermined period after the ignition switch is turned off while the headlight switch remains on.

Abstract: A control circuit for a tone generator that is adapted to cause the tone generator to produce a plurality of readily distinguishable audible sounds, including a chime sound, a pulse tone and a steady tone. The control circuit has particular application for use on an automobile to monitor such conditions as "seat belts buckled", "headlamps on", and "key in the ignition". The control circuit includes three oscillator circuits that are adapted to produce square wave output signals at three different frequencies. The chime sound is generated by pulse width modulating the highest frequency signal and "restriking" the decaying sound at the frequency of the lowest frequency oscillator. The steady tone is produced by driving the tone generator directly with the output signal from the highest frequency oscillator. To generate the pulse tone, the highest frequency oscillator is repeatedly enabled and disabled in accordance with the output signal from the middle frequency oscillator.

Abstract: A digital transmission system comprises a transmitter and a receiver for use in a security system. An alarm code is set by means of switches in both the transmitter and receiver and is indicative of the address or location of a monitored location. The location as monitored contains a sensor which is in either an opened or a closed condition indicative of a secure or unsecure status. The transmitter operates to transmit a digital code for each change in the status of the loop. The code contains bits which define the alarm code or address, while additional bits define the loop status as opened or closed in conjunction with the condition of a battery which is used to power the transmitter. The receiver is adapted to receive the transmitted signal and is operative to compare the transmitted address with the code stored or programmed by the receiver switches. If a valid code is received within a predetermined interval, the receiver operates to decode the loop status by means of an updown counter.

Abstract: In anesthesia apparatus for supplying oxygen and an anesthesia gas through respective flow control valves to a patient breathing circuit a low oxygen flow alarm system is provided. The alarm system includes a restrictor in the pipeline of the oxygen flow control valve and a restrictor in the pipeline of the anesthesia gas flow control valve. A differential pressure sensing unit including a diaphragm assembly responsive to the pressure in the oxygen pipeline and another diaphragm assembly responsive to the pressure in the anesthesia gas pipeline is coupled to the restrictor pipelines. The diaphragm assemblies are opposed to each other and coupled together by a displaceable linkage. Electrical switch means are provided coupled to the linkage to provide an alarm signal when the linkage has been moved to a predetermined position indicating that the oxygen concentration has dropped below a predetermined value. The differential pressure sensing unit includes spring biasing means.

Abstract: An intrusion alarm system and method is provided which includes one or more sound pulse transmitters that are triggered upon the opening of an entryway, such as a door or window, to produce a high-intensity sound pulse having a decibel level above a predetermined minimum. For example, each transmitter may comprise a percussive photoflash unit in combination with a pyrotechnic device which responds to the radiant output of the fired photoflash unit to emit the intense sound pulse. A centralized detector responds to the sound pulse above a predetermined threshold level to produce an alarm signal. Preferably, the detector comprises an electroacoustical transducer arrangement which provides the dual functions of both sound pulse detection and generation of an audible alarm.

Abstract: A restriction indicator having a contactless switch device for indicating a restriction in filter elements of fluid filters having an intake side and a negative pressure side. The restriction indicator includes a photointerrupter having a light emitting device and a light receiving device. The light receiving device provides an electrical signal indicative of increased negative pressure in the negative pressure side.

Abstract: A system for warning an operator when the vacuum in a system, such as a diesel engine air intake system, exceeds a predetermined maximum because of clogging of the air cleaner or other reasons, and when the vacuum falls below a predetermined minimum value indicating loss of air cleaning action as, e.g., because of damage to the air cleaner or because of a hole or leak in the air intake system. The system includes a vacuum gauge having spaced, adjustable electrical contacts, an electrically conductive indicator movable between the contacts, and means responsive to the change in air intake system vacuum to move the indicator; and an electrical circuit having one or more visual or audible warning signal devices. The electrical contacts are connected to the circuit and the indicator is electrically grounded such that when the indicator engages one or the other of the electrical contacts on an unacceptable rise or loss of vacuum, respectively, it closes the circuit to actuate the warning signal device.

Abstract: A repeater is provided for a smoke alarm or similar alarm device which picks up the sound from the alarm device and transmits a coded radio signal to a receiver at a remote location. This receiver includes an integrator set for some convenient time interval to prevent false triggering. In accordance with a preferred embodiment of the invention, the receiver may incorporate a location indicator and be used with a plurality of transmitters.

Abstract: An indicator for evaluating the condition of a brake system defined by a pair of conductors operatively connected to an indicator bulb circuit embedded within the brake lining. One conductor shows when the lining touches the brake drum while the second conductor shows when the lining is excessively thin. The conductor's alignment in the lining is adjustable.