Abstract: A computer implemented method of detecting unauthorized mobile wireless transmitters, comprising using one or more processors adapted for obtaining, from one or more radio frequency (RF) sensors deployed in a monitored location, RF sensory data relating to a plurality of transmissions transmitted by one or more of a plurality of mobile wireless transmitters, detecting a change in a location of one or more of the mobile wireless transmitters by analyzing the RF sensory data, classifying one or more of the mobile wireless transmitters as unauthorized in case the detected location change deviates from one or more mobility rules and outputting an indication of the classification.

Abstract: The application includes a method to control a leakage current protection device in a photovoltaic apparatus, said photovoltaic apparatus being adapted to be electrically connected to an electric power distribution grid having one or more phase voltages at an AC section of the photovoltaic apparatus. The method includes executing a first control procedure to control the leakage current protection device, the first control procedure providing for a comparison of current check values indicative of leakage currents in the photovoltaic apparatus with one or more predefined current threshold values for the leakage currents. The method includes executing a monitoring procedure to check the phase voltages and identify possible relevant positive transients of the phase voltages.

Abstract: A climate status indicator for a vehicle includes a light guide positioned around a vent perimeter. The climate status indicator additionally includes a light device coupled to at least one vent fin. The light guide and/or the light device are configured to provide a visual indicator of a climate status.

Abstract: The present disclosure provides a digital detector apparatus for use with a sensor unit is provided wherein the sensor unit includes an emitter device and a receiver device, the receiver device having a capacitance. The digital detector apparatus comprises at least a first input port, first output port, and a second output port; and an A/D converter circuit wherein an input of the A/D converter circuit is coupled to the first input port for receiving an output of the receiver device; wherein the first output port of the digital detector apparatus is coupled for charging and discharging the capacitance of the receiver device; the second output port of the digital detector apparatus is coupled for driving the emitter device; and the A/D converter circuit derives a sensor output value from the output of the receiver device during a number of charging and discharging cycles. A digital smoke detector and a method of generating an output signal in a digital detector are also provided.

Abstract: A battery management system includes a switching element configured to selectively couple a resistive network in parallel with a capacitor that couples a voltage bus and a ground reference. A controller is programmed to, in response to activating the switching element for a predetermined time, output a diagnostic according to a leakage resistance that is based on a time associated with a predetermined change in a voltage across the capacitor. A time constant is derived from the voltage response and the leakage resistance is derived from the time constant.

Abstract: A charging device includes a current control device configured to receive a first amount of current from a power source. The charging device also includes a ground detection module including a leakage circuit configured to direct a second amount of current to ground to generate a leakage voltage and a comparison circuit configured to detect a connection to ground of the charging device based on the leakage voltage generated. The charging device also includes a controller coupled to the ground detection module and to the current control device. The controller is configured to enable the first amount of current to be supplied to a power storage device of an electric vehicle when the connection to ground is detected.

Abstract: A method and/or system of a breathable air safety system for civilians in a building structure in an emergency. In one embodiment, the safety system includes a supply unit of a structure to facilitate delivery of breathable air from a source of compressed air to an air distribution system of the structure, a fill panel of the structure to provide a pressure of the breathable air such that the pressure is suitable for direct human consumption through a breathable air apparatus coupled with the fill panel, and a routing mechanism of the structure to provide a routing between the fill panel and other fill panels of a particular level through at least one of a wall, a ceiling, and a surface of the particular level of the structure. The safety system may include a communication system of the fill panel to enable communication with security services and/or emergency services directly from the fill panel.

Abstract: A pollution information message system provides a system and method for generating and transmitting pollution information messages. In one embodiment, the pollution information message system employs a transceiver network with a plurality transceivers coupled to monitoring devices. Control room operators receive a pollution information message from an identifiable transceiver. The transceiver, identified by an identification code, indicates a location and the nature of the detected pollution. Other aspects, embodiments, and features are also claimed and described.

Abstract: A system and method for low-cost, fault tolerant, EMI robust data communications, particularly for an EV environment.

Abstract: A system includes a capacitor, a plurality of notification devices connected in parallel with the capacitor, and a controller. The controller is capable of determining capacitance of the capacitor during charge-up of the capacitor, and the controller is capable of determining the wiring impedance of the emergency notification circuit during discharge of the capacitor.

Abstract: A wireless bolt lock remote is disclosed. The wireless bolt lock remote includes a control circuit adapted for use with a bolt lock system and configured to detect a locked state and an unlocked state of a bolt lock, and upon detection of a change in state to wirelessly transfer a status to identity the detected state to an alarm system. The control circuit is wirelessly coupled to the alarm system for wireless communication. The wireless bolt lock remote includes a power source to supply power to the control circuit. Associated systems and methods for remote wireless security for bolt locks also are disclosed.

Abstract: A method and apparatus is provided for minimizing potential security problems and battery power usage in a tracking device used in tracking an associated product while being transported along a route wherein wireless communication may be nonexistent or intermittent. This is accomplished in part by having an accessible database of signal quality and strength at a large plurality of locations along given transportation routes whereby adjustments can be made as to the times for the tracking device to obtain GPS location information as well as for times to report any location and or product status data to a remotely located central station. The ability to predict when, along a transportation route communication problems may occur provides the opportunity to notify appropriate authorities in advance of arriving at the communication gap zones whereby arrangements can be made to alleviate potential problems during transportation through wireless communication “gap or dead” zones.

Abstract: An apparatus for producing an electrosensory sensation to a body member (120). The apparatus comprises one or more conducting electrodes (106), each of which is provided with an insulator (108). When the body member (120) is proximate to the conducting electrode, the insulator prevents flow of direct current from the conducting electrode to the body member. A capacitive coupling over the insulator (108) is formed between the conducting electrode (106) and the body member (120). The conducting electrodes are driven by an electrical input which comprises a low-frequency component (114) in a frequency range between 10 Hz and 500 Hz. The capacitive coupling and electrical input are dimensioned to produce an electrosensory sensation. The apparatus is capable of producing the electrosensory sensation independently of any mechanical vibration of the one or more conducting electrodes (106) or insulators (108).

Abstract: A proximity sensor includes a sense electrode having a first capacitance to ground, wherein the first capacitance varies in response to proximity of an object to be sensed; a first sense circuit which provides a first pulse signal having a pulse width determined in accordance with the first capacitance; a reference capacitor; a second sense circuit which provides a second pulse signal having a pulse width determined in accordance with a second capacitance of the reference capacitor; and a computing circuit which computes a difference pulse by subtracting the second pulse signal from the first pulse signal and provide a pulse of the difference pulse width.

Abstract: A machine and method for anticipatory sensing and intervention to avoid swimmer entrapment, entanglement or evisceration; with a proactive, pre-entrapment, ultrasonic sensor assessing the relative hazard of swimmer proximity to a drain cover. A transducer launches waves into the suction piping and/or drain system, and receives echoes from the drain cover, swimmer limbs, hair or body, and water or wall surface parallel to the drain cover. A transmitter electrically energizes the transducer launching waves into the suction piping and/or drain system. A receiver/processor detects the echoes analog signals from the drain cover and water beyond the pool drain. A Logic and Control element converts the detected signals into reliable information regarding safety/hazard status for a swimmer near a drain. Predetermined logic provides automatic pump shutdown, and alarms as required; including a missing drain cover. A pool alarm mode detects that an object, such as a small child, has fallen in.

Abstract: A method, system and circuit arrangement exchange data and supply power to at least one current sink connected via at least one data line pair to a fire alarm control unit. A pulsed voltage is used as the supply voltage for the current sink connected via at least one data line pair. Useful data is transmitted to the fire alarm control unit between two voltage pulses. The voltage required to transmit the useful data to the fire alarm control unit is used by a capacitor of a circuit arrangement in the current sink charged beforehand by the supply voltage.

Abstract: A capacitive relay takeoff swimming platform sensor system including multiple stations, timing devices and capacitive sensor devices where the presence or departure of a second swimmer on a relay takeoff swimming platform is sensed by the change in capacitance of a sensor mat and compared to the arrival of a first swimmer at a touchpad sensor. The system includes automatic recalibration of sensing, such that presence of a swimmer is sensed and then system recalibrated so as to detect departure of the swimmer. The sensor mat includes an polycarbonate perimeter.

Abstract: An exemplary embodiment of a keypad for building automation may comprise a sensing layer operable to detect user input. The sensing surface configured with a plurality of switching fields assigned to different automation functions. A printed label is layered over the sensing surface for identifying the different automation functions to a user. Control circuitry is operatively associated with the sensing surface. The control circuitry receives user input corresponding to at least one of the switching fields on the sensing surface, and the control circuitry generates a signal for executing the automation function assigned to the switching field at an automation device.

Abstract: A method and system for allocating network bandwidth under alarm conditions. In one aspect, a method of the present invention for allocating network bandwidth to nodes on a network under alarm conditions includes determining that an alarm condition exists for at least one node on the network, and causing an increase in the network bandwidth allocation of the at least one node having the alarm condition. In other aspects, bandwidth requirements of the alarmed node are determined and used in allocating the increased bandwidth.

Abstract: A moving object detecting apparatus, an abnormality alarm apparatus, and a load-carrying compartment opening control apparatus each have an oscillator circuit, an antenna, and a frequency fluctuation detector. If a moving object, such as a human or the like, exists near the antenna when a signal from the oscillator circuit is transmitted from the antenna, the load on the antenna fluctuates due to fluctuations in capacitance involved in the movement of the object. Due to the fluctuations in the antenna load, the oscillating frequency of the oscillator circuit fluctuates. The frequency fluctuations are detected by the frequency fluctuation detector.

Abstract: A circuit for controlling operation of a load, such as an alarm circuit in a fire protection system, in which operation of the load is delayed for an adjustable time period. The load control circuit includes a DIAC for generating a first trigger signal, an SCR which generates a second trigger signal, and a switch, preferably a TRIAC, which provides a supply voltage to the load upon receipt of the second trigger signal. A variable resistor is provided to adjust the time required to generate the first trigger signal.

Abstract: A method and apparatus in a smoke detector for comparing an analog signal voltage to a digital alarm threshold and for converting a digital sensitivity value to an analog test voltage. The analog signal voltage is converted to a digital value by: a) charging a capacitor at a first linear rate directly proportional to the analog signal voltage, for a predetermined time period; b) discharging the capacitor at a second predetermined linear rate to a predetermined threshold; c) counting during the discharging of the capacitor to establish a digital count representing the signal voltage; and, d) comparing the digital count to a an alarm threshold stored in the detector prior to its installation. The digital sensitivity value is converted to the analog test voltage by: charging the capacitor from the first predetermined voltage, at a predetermined rate, for a time period based on the sensitivity and a calibrated conversion factor. This charges the capacitor to an analog voltage representing the sensitivity.

Abstract: A batteryless sensor includes either a micro miniature generator/gear train or a piezoelectric crystal to convert a movement of a door or window to an ersatz V.sub.cc transient power supply to radiate a coded RF signal to a receiver, a distance away. The receiver may monitor a multiplicity of sensors to identify a source of an intrusion.

Abstract: A motion detector having a motion sensitive switch, timing circuit, encoder and radio-transmitting circuit in a housing which may be affixed to a remotely-positioned article; and a decoding and receiving circuit housed in a second housing. The radio-receiving circuit receives the encoded transmitted signal and couples it to a decoding circuit; the decoding circuit is connected to a latch circuit which drives an alarm. The sensitivity of the alarm generation circuits are controlled by a timing circuit, and the alarm may be disabled in order to enable the operator to evaluate the nature of the incoming signals.

Abstract: A line interruption supervisory device for a fire alarm system is capable of reliably carrying out the line supervision even if the line length is long and/or there is a large number of connected fire detectors. To this end, a terminating capacitor is connected across the terminal of a pair of power/signal lines to which fire detectors are connected. A memory first stores the voltage available on the power/signal lines when the line supervision is requested, immediately followed by the interruption by a cut-off circuit of the power supply to a pair of power/signal lines, and further followed by a comparison of the voltage available on the power/signal lines before the power supply interruption with a line voltage available after a lapse of a predetermined time from the power supply interruption by a line interruption discriminating circuit to determine, according to any difference between these voltages, whether there is an open power/signal line.

Abstract: The invention provides an electronic horn for an alarm circuits of the type in which the d.c. power supply for the horn will be of a particular polarity to indicate an alarm condition. The circuit provides a piezo sounder connected across the terminals of the power supply, an inductor connected in parallel with the piezo sounder to form a tank circuit therewith and current modifying means connected in series with the tank circuit to modify the current through the tank circuit in response to the output of an R/S flip-flop which is periodically set by a clock signal at a frequency corresponding to the frequency desired for the fundamental audible tones of the sounder. The duration of the clock output pulse which makes the modifying means conductive must be such that the capacitance of the sounder is charged by the supply before the output of the clock permits a change of state in the flip-flop to make the modifying means nonconductive.

Abstract: An object that is ordinarily held within a receptacle, such as a pen, is monitored to sense removal of the object from the receptacle. Removal of the object initiates a timing cycle. At the conclusion of the timing cycle, an alarm sounds unless the object has been replaced. A reset switch can be provided to reinitiate the timing cycle at any time. If desired, a plurality of object can be monitored, such that removal of any one object begins the timing cycle that leads to the alarm, and termination of the alarm or timing cycle requires replacement of all of the objects.

Abstract: A sheet cutter apparatus includes circuitry for detecting when the blades of the cutter are in an "open" position with their cutting edges separted from each other, and a timer that is initiated when the blades are first opened. If the blades remain open for an excessive period of time, determined by the timer, a warning alarm is generated to remind personnel to close the blades, so that no injuries to fingers, etc., will occur.

Abstract: A motion sensing alarm is disclosed. It is comprised of a time delayed switching circuit connected between a supply circuit and an electronic logic circuit. A triggering circuit is connected between the switching circuit and a false triggering circuit and the electronic logic circuit. An alarm initiating circuit is connected between the electronic logic circuit and an alarm.

Abstract: A device for generating an alarm signal in the event of an abnormality in the environment of a detector includes a pair of signal/power supply lines, a number of detectors for detecting an abnormality, e.g., fire, gas leakage, or burglary, and an alarm receiver including a signal processing circuit for receiving a signal from a detector indicating the presence of an abnormality. The signal process circuit includes a signal storage circuit, and a converting circuit for changing one or a combination of at least two of a polarity, voltage, current, or impedance of a power source if the abnormality persists for a predetermined time. The change in the power source parameter is supplied via the supply lines to a signal holding circuit in the vicinity of the detector. The signal holding circuit is responsive to the changed parameter and changes state, thus providing an indication at the detector that the abnormality has persisted for the predetermined time.

Abstract: An alarm is disclosed herein for providing an indication when a certain condition, such as a door ajar condition of a refrigerator, has existed for a predetermined time. The alarm includes a capacitor, means coupled to the capacitor for charging same while the certain condition is in existence, an indicating device and a voltage sensitive switch coupled to the capacitor and to the indicating device for repetitively partially discharging the capacitor through the indicating device when the charge on the capacitor reaches a particular level. A series of alarm pulses are thereby developed by the indicating device once the certain condition has existed for the predetermined time whereby the alarm pulses are separated by equal intervals substantially shorter than the predetermined time. The alarm of the instant invention is simple in construction and inexpensive.

Abstract: The subject of the invention is a circuit for monitoring the charge state of a battery for supplying voltage to an electrical consumer through a mode selector switch which may be switched from an OFF-state for disconnecting the electrical consumer from the battery into an ON-state for connecting the electrical consumer with said battery whereby in said ON-state different modes of operation of said electrical consumer are possible. The charge state of the battery is determined when the mode selector switch is in the ON-state and, when the voltage drops below an adjustable threshold value, an acoustic and/or optical indication is triggered after the electrical consumer is switched off. The circuit in the ON-state consumes only a very slight amount of energy and no additional energy in the OFF-state. In addition to the mode selector switch for switching the electrical consumer on and off, no battery test button or additional battery test position of the mode selector switch is required.

Abstract: A box formed with an aperture in which a photosensitive cell is secured includes an electronic circuit connected to be fed by the electrical signal produced by the photosensitive cell when the latter is irradiated by ambient radiation. Said electronic circuit comprises a delay circuit adapted to receive the signal and arranged to produce a control signal when the cell has been irradiated for a predetermined time interval; an audible signal generator received in the box opposite apertures and connected to produce an audible signal in response to the control signal; and a circuit adapted to interrupt the audible signal after a predetermined time interval so that the audible signal is of predetermined duration.The box has means for securing it to an object which is required not to be lost accidentally, e.g. keys, a wallet, a diary, etc. A cover can be provided for being placed over the cell to protect it and keep away external radiations when the reminder device is not required to be operative.

Abstract: A toilet reservoir fill alarm including water level sensors which can be positioned in the water reservoir tank of a flush toilet to detect the presence or absence of water at a desired level. A switch responds to the water level sensors and produces a control signal during the absence of a desired level. The control signal operates a timing circuit in order to produce an output signal at the termination of a predetermined time interval. Responsive to the output signal is an alarm circuit. In this manner, an alarm will sound should the toilet tank reservoir not refill during the predetermined time interval following the flushing of the toilet.

Abstract: In a fire detector that includes a sensor for producing an output voltage corresponding to smoke concentration, temperature, etc., there is provided a charge-and-discharge circuit to be reset by the turning ON of a switching circuit which is made ON at a fixed voltage. The output of the charge-and-discharge circuit and the output of a sensor are applied to the switching circuit to vary the ON period of the switching circuit corresponding to the output voltage of the sensor. Any irregularity in the sensor can be monitored by changes in the ON period.

Abstract: A visual display system detects and continuously displays the location of a breach in a protected building or secure area. Each of a plurality of exclusive OR gates is connected to a separate reed-type sensor switch. Each exclusive OR gate output is connected to a flip-flop network, each of which in turn is connected to a light emitting diode. Activation of a sensor switch results in lighting only of the light emitting diode associated with the area breached. A mechanism is also provided for preventing the generation of false alarms by transients or inadvertent momentary opening of any of the sensor switches.

Abstract: A passive personal alarm device is activated by release of a spring-loaded button switch which, when held down, opens an otherwise closed circuit. A time delay element in the circuit prevents sounding of the alarm for a predetermined period in the event of an accidental release of the actuating button. The button is released, either purposefully or inadvertently, during an attack and the alarm is sounded after expiration of the time delay. Once activated, the alarm device can be deactivated only by repositioning a number of coded switches in a pattern known only to the alarm user.

Abstract: A low fuel indicator system 10 for a motor vehicle comprises a light-emitting indicator 12 which is energized or de-energized by an output signal derived from a voltage comparator 14 which receives a reference voltage from a reference voltage source 20 and a variable voltage signal from a time delay circuit 22, which variable voltage signal is derived from a voltage signal generated by a fuel level sensor in a fuel tank of the vehicle. The light-emitting indicator 12 is energized when the fuel level in the fuel tank falls below a predetermined low level, and time delay circuit 22 operates to isolate the voltage comparator 14 and light-emitting indicator 12 from temporary variations in fuel level produced by "fuel-slosh" in the fuel tank caused by variations in the motion or orientation of the motor vehicle.

Abstract: A pressure transducer, such as a microphone, is placed in proximity to the blades of a fan, such as a fan used to cool electronic equipment. As each blade passes the transducer, a pressure wave is generated that is converted into an electrical pulse by the transducer. Circuitry responsive to those pulses signals an alarm if the fan is not operating properly.

Abstract: A fire sensor discriminates between fires and the flash caused by a projectile piercing the wall of a protected area. The sensor system comprises first and second radiant energy detectors, each sensitive to radiation within different spectral bands. Each detector is coupled to a control signal means for generating a control signal when the radiation sensed exceeds a predetermined amplitude. A third control signal means is responsive to the first and second detectors, and is operative to generate a third control signal whenever the ratio of the amplitude of the energy sensed by the first detector to the amplitude of the energy sensed by the second detector is less than a predetermined value; not generate the third control signal whenever the ratio of amplitude exceeds the predetermined value; and delay generation of the third control signal for a predetermined period of time after the ratio of amplitudes falls below the predetermined value.

Abstract: A motion detection system is disclosed which utilizes a lens or other imaging device to be responsive to motion in a particular field of view in a room, for example, and pass illumination to a photocell. The photocell or a screen in front thereof establishes image distortion so that there is a nonuniform electrical output from the photocell upon motion of objects in the given field of view. The nonuniform electrical output establishes pulses which are passed to a timer and continually resets the timer so long as there is motion detected. Upon discontinuance of any motion in the field of view, no further pulses are passed to reset the timer, and the timer times out to de-energize an electrical load. This may be an electrical lamp illuminating the field of view, or it may be an electric soldering iron or typewriter which is de-energized when the person has left the room.

Abstract: Circuit arrangement of a staircase lighting time switch offers a possibility of an automatic reduction of the light power of lamps lighting the staircase whereby the user is warned that the time of the switch is running out. The time period of full power as well as the time period of reduced power can be set separately. Each activation of the push-button switch prolongs the operation of the circuit for the operation time to which it is adjusted.

Abstract: A switch is placed on a bed, chair, or other object and is maintained in closed condition so long as a patient occupies the bed, chair, or other object and continues to exert sufficient weight on the switch. When the weight acting on the switch is relieved, the switch opens to cause an associated circuit to give an immediate audible alarm. The circuit also causes a visible alarm to be given shortly thereafter. The circuit is powered by a D.C. battery and includes a low voltage monitor which causes the audible alarm only to be given when the battery voltage drops below a certain level indicative of the need to replace the battery. A three position control switch establishes off, on, and test modes of operation. The patient monitoring switch comprises a tape switch arranged in a T-shape configuration, and the switch is foldable in half for use with a chair.

Abstract: An exposure detecting device comprising a radiation detector means providing an output signal responsive to the intensity of received ultraviolet radiation, a storage means receiving the output signal of said detector means and providing an output signal which increases as a function of the signal received and its duration, and decreases in the absence of a received signal as a predetermined function of time. A sensitivity control means provides a reference signal, and comparing means receives the output signal of said storage means and the reference signal of said sensitivity control means and delivers an output signal when the storage means output signal exceeds a predetermined value with respect to the reference signal. Alarm means is activated upon receiving an output signal from said comparing means providing an alarm.

Abstract: A fire alarm system comprises a central control station feeding through a plurality of parallel supply lines a direct current voltage to a corresponding plurality of remote alarm stations. Each station has a fire sensor including a reference ionization chamber and a measuring ionization chamber, both chambers being connected in series between the two supply lines and having a common intermediate electrode. A field effect transistor has a gate electrode connected to the intermediate electrode of the ionization chambers and a source drain conducting channel the conductivity of which is controlled by the gate electrode. The input resistance and the input capacitance of the field effect transistor is connected parallel to the reference ionization chamber and defines therewith a first relatively short time constant of about two seconds.

Abstract: Apparatus for disabling an alarm after a predetermined operating period employs a relay which is operated by a gate circuit. A contact of the relay applies operating potential to an alarm. An oscillator energizes a counter circuit and after a predetermined selectable period, the counter circuit inactivates the relay via the gate to cease alarm operation.

Abstract: An electrical system for use on aircraft and including a manually operated master switch for connecting a d.c. power supply to a supply bus that feeds electrical equipment on the aircraft. Energized by the supply bus is a monitor having a delayed output that activates an alarm indicating a closed condition of the master switch. The monitor is disabled by a sensing circuit that responds to the presence of electrical pulses generated on the bus by the aircraft's alternator. Upon a failure to open the master switch after the aircraft's engine has been stopped, the absence of alternator charging pulses on the bus prevents the sensor from de-activating the monitor which after a predetermined time delay energizes the alarm to warn the pilot of the condition that would result in discharging of the battery.

Abstract: A current detecting apparatus wherein when a wire is energized, a reed switch comes into operation in response to the magnetic lines of force generated concentrically around the wire to detect the presence of a current flow in the wire. The current detecting apparatus may be easily attached on and removed from a wire.

Abstract: A sensing means is connected to the input of an electronic circuit for triggering a signalling means. The electronic circuit includes a continuous differential amplifier whose two inputs (-) and (+) are connected to the terminals of the sensing means. The input terminals are also connected by means of at least two switches to voltage sources in such a way that, by closing one of the switches, the polarity of the input terminal in question is reversed, to disable the detection device, and, by closing the other switch means, there is an increase, with the same sign, in the polarity of the input in question, for triggering the signalling means.

Abstract: In burglar alarms in which ultrasonic waves are transmitted into a protected space and reflected to a receiver which detects disturbances in the reflected waves caused by an intruder to actuate the alarm, the alarm might be actuated not only by an illegal intruder but also by a short pulse-type vibration. For such reason, the present invention is so designed not to be actuated by a short vibrations with a timer being inserted so as to be actuated only by an input signal continuing for more than a fixed time (practically 0.7 seconds). Further, when such signal continues for more than a fixed time and contains a sound of a telephone bell containing a high frequency component, the high frequency component controls a switching element, permitting a setting time of the timer to extend over a telephone ringing time, thus arranging the alarms not to operate.