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EP0814445B1 - Système d'alarme automatique avec analyse d'un signal de surveillance - Google Patents

Système d'alarme automatique avec analyse d'un signal de surveillance Download PDF

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Publication number
EP0814445B1
EP0814445B1 EP19970201449 EP97201449A EP0814445B1 EP 0814445 B1 EP0814445 B1 EP 0814445B1 EP 19970201449 EP19970201449 EP 19970201449 EP 97201449 A EP97201449 A EP 97201449A EP 0814445 B1 EP0814445 B1 EP 0814445B1
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EP
European Patent Office
Prior art keywords
supervision
signal
station
receiving station
sensitivity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP19970201449
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German (de)
English (en)
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EP0814445A3 (fr
EP0814445A2 (fr
Inventor
Francis Carmine Marino
Thomas Paul Schmit
Kenneth Lyle Addy
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Honeywell International Inc
Original Assignee
Honeywell International Inc
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Filing date
Publication date
Priority claimed from US08/650,292 external-priority patent/US5828300A/en
Priority claimed from US08/685,716 external-priority patent/US5748079A/en
Priority claimed from US08/685,539 external-priority patent/US5801626A/en
Application filed by Honeywell International Inc filed Critical Honeywell International Inc
Publication of EP0814445A2 publication Critical patent/EP0814445A2/fr
Publication of EP0814445A3 publication Critical patent/EP0814445A3/fr
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Publication of EP0814445B1 publication Critical patent/EP0814445B1/fr
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/12—Checking intermittently signalling or alarm systems
    • G08B29/123—Checking intermittently signalling or alarm systems of line circuits

Definitions

  • the present invention relates to a receiving station for use in a communication system and to a method of checking for an effective power margin in a communication system.
  • RF wireless security systems such as those manufactured by ADEMCO
  • RF radio frequency
  • Most radio frequency (RF) wireless security systems available today generally employ a multiplicity of transmitter products which transmit information to a common receiver/control.
  • the information transmitted typically describes the state of various transducers associated with each transmitter, such as smoke, motion, breaking glass, shock and vibration detectors; door, window and floor mat switches; etc.
  • These transmitter products are designed to be low in cost and are typically send-only devices, as opposed to send/receive, or transceiver, devices which are significantly more expensive.
  • the transmitters are required to transmit periodic supervision transmission signals in order for the control to monitor proper operation of all of the transmitters in a given system.
  • the supervision signal (as well as an alarm signal) has a unique identification code embedded in its data message, which serves to identify to the system control which particular transmitting device has sent that supervision (or alarm) message.
  • the transmitter identification code is supplied to the system control for further processing.
  • the RF wireless system must also comply with more stringent regulations, such as the Underwriters Laboratories regulation UL864.
  • This regulation additionally requires that the supervision signal be reduced in transmission power level below that of the alarm (normal, non-supervision) signal transmission by a minimum of 3dB or by other equivalent means, to ensure that the alarm signal has an effective power margin over that of the periodic supervision signals from each transmitter in the system.
  • US-A-4 754 261 discloses an apparatus for evaluating installation of components of a wireless alarm system.
  • a central station can receive alarm signals from a plurality of satellite stations. During installation, the central station can be manually placed in an installation mode in which a characteristic of the received alarm signal is impaired so that a received signal of greater quality than in a normal operating mode is required to trigger the alarm.
  • an alarm system that utilizes automatic testing of the received supervision signal without modifying its receive sensitivity or other operational parameter for subsequent messages, but rather by performing such tests in real-time on the first detected supervision message. It would therefore be advantageous to employ an alarm system which receives the system supervision messages at a sensitivity below a normal alarm signal and therefore ensures that the alarm signal has an effective margin over that of the periodic supervision messages from each transmitter in the system, without modification to the transmitters already in commercial use.
  • an alarm system that utilizes a method of measuring the signal strength of received messages and to compare the measured signal strength against a predetermined threshold, which must be exceeded for the supervision message to be accepted as valid.
  • a receiving station (6; 6a; 6b) for use in a communication system, which receiving station comprises receiving means (20; 20a) for receiving signals from a remote transmitting station, the receiving station being operable to determine whether or not there is an effective power margin for reception of signals, characterised by control means (30, 32; 38a, 42a; 38b, 42a) that can determine whether a signal received from said remote transmitting station is of a supervision or a non-supervision type, and that performs a test in response to identification of a supervision signal to determine whether or not a non-supervision signal from that remote transmitting station would have the effective power margin over said supervision signal.
  • a method of checking for an effective power margin in a communication system comprising a receiving station (6; 6a; 6b) having receiving means for receiving signals of a supervision and a non-supervision type from at least one remote transmitting station (4), which method comprises the steps of:
  • a first aspect of the present invention is based on the premise that instead of reducing the maximum allowable power of the periodic supervision signal transmissions, an equivalent means is to reduce the receiver sensitivity by an amount equivalent to reducing the transmitting power by 3dB, but only during receipt of supervision signals, and to provide full receiver sensitivity when receiving non-supervision alarm signals.
  • the first requirement of the receiver in this first aspect of the invention is that it have the ability of changing the receive sensitivity by at least 3dB to meet the applicable regulatory agency requirements.
  • the receiver implemented in the present invention is a superheterodyne-type receiver and the circuit used to alter its sensitivity is common knowledge to those skilled in the art of narrow-band, short-range, RF superheterodyne receivers, and need not be discussed in any detail here. It is sufficient to say that the receiver sensitivity is altered between two predetermined values by the logic 1 or logic 0 state of a microprocessor output connecting to that portion of the receiver circuits which determine the receiver sensitivity. This allows the receiver sensitivity to be under control of the microprocessor software.
  • a second aspect of the present invention is based on the premise that instead of reducing the radiated power of the transmitted periodic supervision signals, it is equivalent to receive supervision signals at reduced sensitivity while maintaining full sensitivity for alarm transmissions.
  • the first requirement of the receiver is that it have the ability to receive signals at two distinct sensitivity levels, at least 3dB different to meet applicable regulatory agency requirements.
  • the receiver implemented in the present invention uses a superheterodyne architecture, although those skilled in the art will recognize that all receiver types may be applied equally well in this invention. It is important to note that the receiver sensitivity is most cost-effectively controlled by means of introduction of a threshold or clipping level in the video processing circuitry after the incoming RF signal is demodulated and reduced to its original baseband content.
  • the video processing circuit output is two identical baseband signals except that one of the signals has been subjected to a 3dB higher threshold than the other.
  • the signal received at high sensitivity is used by the microprocessor to obtain timing and synchronization information during a preamble portion of the message, the timing information is then used by the microprocessor to clock-in the subsequent data and CRC portions of the message into both microprocessor input ports.
  • the signal received into the reduced sensitivity port is stored in RAM in the microprocessor.
  • the signal received at the high sensitivity port is checked for proper CRC and it is determined whether or not the message is of a supervision type. If the message is a non-supervision message then it is passed directly to the control panel for further processing. If the CRC is good and the message is a supervision type, then the stored data in RAM from the reduced sensitivity port are read and the CRC is computed, if it is correct, and is identical to (correlated with) the message received at the high sensitivity port, then this message is passed to the control for further processing. If the CRC does not compute or the stored message does not match the high sensitivity message, then the message is not processed any further, and the supervision transmission fails to be received.
  • a third aspect of the present invention is based on the premise of a generating an RSSI (received signal strength indication) signal indicative of the signal strength of the received signal, and determining if the received signal is a supervision signal or a non-supervision signal.
  • RSSI received signal strength indication
  • an alarm system 2 which includes a receiver/control unit 6 in communication with a plurality of remote devices 4, each of which comprise an alarm sensor and a data transmitting unit.
  • the alarm sensors are well known in the prior art and include, for example, motion detectors, fire or smoke sensors, glass breakage sensors, door or window entry sensors, and the like.
  • the alarm system 2 operates in a so-called "wireless” fashion by electromagnetic wave transmission (radio frequency in particular) between the remote devices 4 and the receiver/ control unit 6.
  • the transmitter units housed within each remote device 4 are also well known in the art, and transmit supervision and alarm message signals, to be described below, by modulating a high frequency RF signal (e.g. 345 MHz).
  • the modulated RF signal is received, processed and decoded by the receiver/ control unit 6 so that the control unit is provided with the data from the remote devices 4 and may act accordingly; e.g. by sounding an alarm speaker, dialing a police or fire station, etc.
  • a high frequency RF signal e.g. 345 MHz
  • the modulated RF signal is received, processed and decoded by the receiver/ control unit 6 so that the control unit is provided with the data from the remote devices 4 and may act accordingly; e.g. by sounding an alarm speaker, dialing a police or fire station, etc.
  • U.S. Patent No. 4,754,261 to Marino which is owned by the assignee of the present invention and is incorporated by reference herein.
  • the remote devices 4 are configured to transmit supervision signals and alarm signals in accordance with protocol known in the art.
  • the supervision signals function to provide periodic "test" signals to the receiver/control unit 6 for the purpose of ensuring that each remote device 4 configured with the system 2 is in proper communication with the receiver/ control unit 6. Since it is possible in this type of system that a remote device 4 may only transmit an alarm signal at a time of an emergency (i.e. when a window associated with the sensor is broken), it is imperative that the system 2 maintain a periodic method of ensuring that a device 4 is in proper communication with the receiver/ control unit 6 so potential problems may be attended to promptly.
  • a supervision signal is periodically sent from each remote device 4 in the system to the receiver/control unit 6 for monitoring purposes.
  • a supervision transmission sequence typically consists of a single pentad, which is a single group of five identical messages, as shown in section A of Figure 2. Each message is approximately 20 ms in duration and is repeated every 100 ms as shown in Figure 2.
  • a normal, non-supervision alarm signal which is transmitted typically only when a change in status of the alarm sensor occurs (e.g. when a door is opened), consists of a double pentad, which is two groups of five identical messages separated in time by approximately 1 second. This is shown in section B of Figure 2.
  • Each identical message is 64 bits long and has a 16-bit preamble, 24 bits of transmitter serial number or keypad data, a single 8-bit status byte, and a 16-bit CRC (Cyclical Redundancy Character), as shown in section C of Figure 2.
  • the status byte contains 8 data bits, shown as D1-D8 in section D of Figure 2, which convey specific information.
  • D1-D4 represent the state of up to 4 sensor inputs to that transmitter
  • D5 indicates the state of that transmitter's battery
  • the receiver circuitry is provided with coded information from the transmitter unit which enables it to determine if the message is part of a supervision signal or part of a normal, non-supervision alarm signal.
  • the receiver when the receiver detects that the present message is part of a supervision pentad, the sensitivity of the receiver is immediately reduced.
  • the lowered sensitivity level will remain in effect until a subsequent supervision message is properly received at this lowered level which matches the first message received at the full sensitivity level, or following a pre-determined time delay of 600 ms, whichever occurs first. If during this interval of reduced sensitivity, a supervision transmission is successfully received which does not match that which initiated the interval (i.e. the message stored in the receiver), then the supervision message for the non-matching transmitter ID is immediately sent to the control unit for subsequent processing.
  • a signal (alarm or supervision) to be received from a different remote device 4 during the time that the receiver is in reduced sensitivity as a result of detecting the reception of a supervision signal. That is, a second received signal may be interleaved with a first received signal. In order for the receiver to properly process the interleaved second signal, the timeout period used for waiting for the next supervision message must be greater than the time for one pentad but less than the time before the second pentad of an alarm transmission can start.
  • FIG. 3 A typical scenario is illustrated in Figure 3 in which the first supervision message results in a reduction of the receiver sensitivity level and the second supervision message, matching the first message, is properly received.
  • proper reception of the supervision message at the reduced sensitivity level has been established for that particular transmitter allowing the receiver to send the supervision message for that transmitter ID to the control.
  • the continuation of the lowered sensitivity level if the second, third, etc. message fails to be properly received due to the lowered sensitivity. If all of the remaining four messages fail to be properly received at this reduced level, the required margin for that transmitter is assumed inadequate. In that case the supervision message for that transmitter ID will not be sent to the control. The control will thus be in receipt of only those supervision messages per transmitter ID in the system which can be received at the reduced sensitivity level, meeting the UL864 requirement.
  • step S1 the (RF) input signal is processed to provide a digital data signal.
  • step S2 the digital data signal is decoded to analyze the status bit D6 to determine if the message is supervision or non-supervision alarm. If step S3 determines the message to be non-supervision, then the message is sent to the control for processing at step S4 and the process is ended. If however, the message was determined to be a supervision message, then it is stored in a temporary buffer at step S5, and the receiver sensitivity is reduced by 3dB at step S6.
  • a timeout clock which in the preferred embodiment is 600ms as explained above, is then initiated at step S7. The process loops in a wait state via steps S8 and S11 until the timeout expires at step S8 or a new message is received at step S11.
  • the timeout has expired without a new message being received while the receiver is in the reduced sensitivity state, then the stored message is ignored at step S9, the receiver sensitivity is increased back to normal at step S10, and the process is ended.
  • the supervision message since the supervision message was not properly received and detected while the receiver was in the reduced sensitivity state, then the transmitter ID associated with that supervision message is, in effect, thrown out, and the receiver control unit is never informed of its initial reception at the full sensitivity level.
  • the supervision signal was strong enough to be detected at the normal sensitivity level, it could not be received at the effective reduction of 3dB in signal strength, and the UL864 test is not met for that remote device 4.
  • step S11 If however, a new message is received at step S11, then it is analyzed at step S12 to determine if it is the same as the message stored in the temporary buffer; that is, if it is from the same transmitter device or if has been received from a different transmitting device which has in effect interleaved its message stream with that of the originally received message. If the message is from a different transmitter, then it is sent to the control by step S13 (since it was successfully received at the reduced sensitivity level), and the wait state continues with steps S8 and S11. The timeout clock is not reset, since the receiver is still waiting for the next supervision message which matches that which initiated the reduction in sensitivity. Thus, if a new message matching the stored message is not received within the timeout period, the receiver sensitivity is increased to normal and the process ends with the stored message being ignored.
  • step S12 determines that the new message matches the stored message, then the test has passed and the message is sent to the control by step S14 for subsequent processing.
  • the receiver sensitivity is increased back to normal and the process is exited.
  • FIG. 5 illustrates the circuit block diagram for the receiver/ control unit 6 of the first aspect of the present invention.
  • An RF signal is received at the antenna 20, and is filtered by section 22 and demodulated by section 24 in conjunction with a 355.7MHz oscillator 26 in accordance with techniques well known in the art.
  • a demodulated baseband video signal 28 is fed to a video processor circuit 30, which has programmable sensitivity for accomplishing the objectives of this invention.
  • a microprocessor 32, along with appropriate ROM memory device 34 configured to store the program embodied by the flowchart of Figure 4 is connected to the video processor 30 for supplying appropriate control signals thereto for controlling the receiver sensitivity.
  • control signal 36 is changed to indicate to the video processor that the sensitivity of the receiver unit should be reduced by 3dB.
  • This control signal is again toggled in accordance with processing described above in order to return the receiver sensitivity to normal when required.
  • the transmitter identification data is sent to the control unit (not shown here) for subsequent processing as described above via the ECP data bus 38, which is a four line interface comprising a ground and power line, and send and receive data lines in accordance with techniques well known in the art.
  • Control signal 40 allows for manual control of the receiver sensitivity, if desired, by means of the keypad panel 8 or the like, in order to place the system into a test mode for device installation purposes as described in the aforementioned Patent No. 4,754,261.
  • the preferred embodiment of the first aspect of the present invention has been described with reference to the reduction of the receiver sensitivity in order to provide an impaired transmission/reception function and thus test the margin of operation of the system to ensure it will perform according to applicable regulatory requirements. It is contemplated that this may also be implemented by modifying other operational parameters of the receiver in order to obtain similar results. For example, as disclosed in the above-mentioned U.S. Patent No. 4,754,261 to Marino, the clipping level of a shaping circuit used in conjunction with the receiver may be altered as a result of the detection of a supervision message, the baud rate of the receiver may be modified in order to put a higher demand on the system operation, etc.
  • supervision messages in a supervision signal which are identical to each other
  • supervision messages which correlate to each other in some predetermined fashion, rather than requiring them to be identical.
  • supervision messages may be encoded with indicia representing the source of transmission, but may differ from each other in other ways.
  • the system can be easily adapted to analyze the relationship between supervision messages to determine if they are properly correlated, thus determining that they were transmitted from the same source and allowing further processing of the message where appropriate.
  • FIG. 1 again illustrates the block diagram of the system utilized by this second aspect of the invention; however, receiver/ control unit 6a is utilized (as shown in Figure 6) rather than the receiver/ control unit 6 of the first aspect of the invention.
  • the message format utilized by the second aspect of the present invention is illustrated and operates as described above.
  • the microprocessor decoding algorithm determines the necessary timing information required for subsequent decoding of the data portion and CRC of the message. This timing and initial decode is determined using the high sensitivity port of the microprocessor shown in Figure 6.
  • This method does not rely for its success on multiple supervision or alarm messages to be sent at each alarm event, nor is this method adversely affected by multiple transmissions.
  • FIG. 6 illustrates the circuit block diagram for the receiver/ control unit 6a of this second aspect of the present invention.
  • the receiver 6a comprises an antenna selection circuit 20a, an RF filter 22a, a low noise amplifier 24a, a second RF filter 26a, a mixer 28a, a local oscillator 30a, an IF filter 32a, an IF gain and demodulation circuit 34a, and a video filter 36a, which are all well known in the art of RF receivers.
  • a demodulated baseband video signal is fed from the video filter 36a to a video processing circuit 38a and threshold circuit 40a which function to provide two outputs which have been subjected to different sensitivity thresholds.
  • These data outputs are connected to two input ports of a microprocessor 42a.
  • the reduced sensitivity port is followed by an adequately sized buffer 44a to store the received data should the data be from a supervision signal and further correlation is required.
  • the input signal is received and processed by the aforementioned components, and two data signals are derived; one at full, or normal receiver sensitivity, which is input to the microprocessor at port 12, and a second signal at reduced sensitivity, which is input to the microprocessor at port I3.
  • the low sensitivity data message is stored in the RAM buffer 44a.
  • the microprocessor examines the D6 bit of the full sensitivity signal input at I2. If it is determined to be a non-supervision signal, then the reduced sensitivity data message stored in the RAM 44a is ignored, and the full sensitivity message from I2 is sent to the control.
  • the microprocessor 42a compares the low sensitivity message stored at RAM 44a with the full sensitivity message, and if they are correlated, then the test has passed and the message is sent to the control. If however, the signals are not found to be correlated, then they are ignored, the test is considered to have failed, and the control is not provided with information that the supervision message were received.
  • correlation of the reduced sensitivity supervision signal and full sensitivity supervision signal is found when the two signals match identically.
  • this second aspect of the invention has been described with reference to a system wherein a single message is transmitted at each transmission event and includes in the message a specific bit to designate a supervision message.
  • a message is often repeated to improve probability of reception and in addition a specific supervision bit may not be included.
  • a supervision transmission may be differentiated from an alarm transmission by the number of repeats of each message.
  • a supervision message be repeated less often than an alarm message.
  • the system described in the present invention will discern whether a message is a supervision type by counting the number of repeats of a received message before deciding whether or not to perform the comparison of low sensitivity and high sensitivity messages.
  • FIG 8 illustrates the detailed schematic of the dotted line portion of Figure 6.
  • IF/demodulator integrated circuit 34 which in the preferred embodiment is a Philips NE614, utilizes the IF input signal and provides at its output a demodulated data signal to the low pass filter 36a formed by R1 and C1.
  • the low pass filter 36a reduces the noise content of the video output signal.
  • the filtered video signal is then AC coupled via capacitor C2 to the non-inverting inputs of the U3 and U4 comparators (LM339), which quantize the signal to a logic level suitable for input to the microprocessor 42a.
  • the combination of R4 and R5 form a voltage divider, which sets a slicing level for the reference voltage applied to the inverting input to the U3 comparator.
  • Capacitor C3 provides an AC ground for the U3 comparator reference input.
  • the reference voltage applied to the inverting input on comparator U4 is modified by means of injection of additional current via resistor Ry.
  • the reference voltage to U4 is offset by an amount determined by the values of Rx and Ry.
  • Ry will be much larger than Rx or may be replaced by a true current source.
  • each comparator U3, U4 are input to the microprocessor 42a input ports I2 and I3, respectively.
  • the microprocessor in the preferred embodiment is a COP881 available from National Semiconductor.
  • the output from U3 is fed to port I2 of the microprocessor, and is the normal sensitivity signal.
  • the output from U4, which has been subjected to a higher comparison threshold than that at U3, is fed to port I3 of the microprocessor. This represents the low sensitivity input signal, which is stored in an internal RAM 44a for subsequent comparison if desired, as described above.
  • the microprocessor 42a may optionally control the threshold applied to U4 with a transistor switch TR1 and Rz, as shown in the optional control circuit of Figure 8.
  • the threshold voltage applied to the inverting input of comparator U4 may be varied by programming an appropriate data bit D0. When D0 is a low logic level, then the transistor TR1 is in the off state, and the threshold applied to U4 is unchanged. When, however, the D0 bit is set to a high logic level, then the transistor TR1 is turned on, and the reference voltage at U4 is varied in accordance with the value of the resistor Rz.
  • the threshold for analyzing supervision signals as described herein may be varied via software control, and may be varied for any particular data message received from a transmitter.
  • each additional control circuit may vary, and each individual control circuit 46 may be controlled by a different bit output from the microprocessor 42a (e.g. D1, D2, etc.). As such, a graduated threshold may be available for use with different environments by programming the appropriate bit to control the desired control circuit 46a and change the reference voltage accordingly.
  • FIG. 1 illustrates the block diagram of the system utilized by this third aspect of the invention; however, receiver/ control unit 6b is utilized (as shown in Figure 9) rather than the receiver/ control unit 6 of the first aspect of the invention or receiver/control 6a of the second aspect of the invention.
  • the message format utilized by this third aspect of the present invention is illustrated and operates as described above.
  • a decoding algorithm implemented with a microprocessor determines the necessary timing information required for subsequent decoding of the data portion and CRC of the message.
  • FIG. 9 illustrates the circuit block diagram for the receiver/ control unit 6b of this third aspect of the present invention.
  • the receiver/ control unit 6b is similar to the receiver/ control unit 6a, and like reference numerals are used for like components accordingly.
  • the receiver 6b comprises an antenna selection circuit 20a, an RF filter 22a, a low noise amplifier 24a, a second RF filter 26a, a mixer 28a, a local oscillator 30a, an IF filter 32a, an IF gain and demodulation circuit 34a, and a video filter 36a, which are all well known in the art of RF receivers.
  • a demodulated baseband video signal is fed from the video filter 36a to a video processing circuit 38b.
  • the video processing circuit 38b provides a received signal strength indication (RSSI) signal 39 in analog format which is indicative of the signal strength of the received signal.
  • RSSI measurement circuits are well known in the art, as set forth for example in U.S. Patents No. 4,620,114; 5,390,365; and 5,423,064.
  • the video processing circuit 38b also outputs to a port I3 on the microprocessor 42a the processed received signal.
  • the analog RSSI signal 39 is processed by an A/D converter 40b, well known in the art, and the resulting digital data word indicative of the signal strength of the received signal is input to the microprocessor port G5 for further processing.
  • the A/D port is followed by an adequately sized RAM buffer 44a to store the digital RSSI data word should the data message on signal 41 be determined to be a supervision type and further processing is required.
  • the input signal is received and processed by the aforementioned RF components, and two data signals are derived; the actual data signal 41, which is input to the microprocessor 42a at port 13, and the digital RSSI data word, which is input serially to the microprocessor at port G5.
  • the RSSI data word is then stored in the internal RAM buffer 44a.
  • the microprocessor examines the D6 bit of the signal input at I3. If it is determined to be a non-supervision (alarm) signal, then the RSSI word stored in the RAM 44a is ignored, and the message from 13 is sent to the control.
  • the microprocessor 42 compares the RSSI word stored at RAM 44a with a predetermined threshold stored in a non-volatile buffer 45, and if the RSSI word is above the predetermined threshold, then the test has passed and the supervision message is sent to the control. If however, the RSSI word is not above the predetermined threshold, then the received signal is ignored, the test is considered to have failed, and the control is not provided with information that the supervision message was received. Thus, the transmitter identification data and other status data are sent to the control system if the message is an alarm type or if it is a supervision type received with adequate signal level.
  • the threshold value used for comparison against the measured RSSI word may be ascertained in various ways.
  • the RSSI threshold may be preset at the factory by typical programming techniques.
  • the RSSI threshold may be programmed by the system installer, who may take measurements during initial operation of the system to determine the proper threshold to use in accordance with the particular environment.
  • the microprocessor may be configured with techniques known in the art to make certain measurements of received signals, and determine an average threshold to use accordingly.
  • FIG 11 illustrates the detailed schematic of the dotted line portion of Figure 9.
  • IF/demodulator integrated circuit 34 which in the preferred embodiment is a Philips NE614, utilizes the IF input signal and provides at its output a demodulated data signal to the low pass filter 36a formed by R1 and C1.
  • the low pass filter 36a reduces the noise content of the video output signal.
  • the filtered video signal is then AC coupled via capacitor C2 to the non-inverting input of the U3 comparator (LM339), which quantizes the signal to a logic level suitable for input to the microprocessor 42a.
  • the combination of R4 and R5 form a voltage divider, which sets a slicing level for the reference voltage applied to the inverting input to the U3 comparator.
  • Capacitor C3 provides an AC ground for the U3 comparator reference input.
  • the output signal of comparator U3 is input to 13 of the microprocessor 42a.
  • the microprocessor in the preferred embodiment is a COP881 available from National Semiconductor.
  • the output from U3 is fed to port I3 of the microprocessor, and is at the normal sensitivity level.
  • the filtered demodulated data signal is also input to an analog-to-digital (A/D) circuit 40b, which provides a digital output representative of the input signal in accordance with techniques well known in the art.
  • A/D analog-to-digital
  • a Texas Instruments TLC549I is used.
  • a serial digital data word is then input to the port G5 of the microprocessor 42a for storage in the internal RAM 44a and subsequent analysis as described above.
  • a single message is transmitted at each transmission event and includes in the message a specific bit to designate a supervision message.
  • a message is often repeated to improve probability of reception and in addition a specific supervision bit may not be included.
  • a supervision transmission may be differentiated from an alarm transmission by the number of repeats of each message.
  • a supervision message be repeated less often than an alarm message.
  • the system described in the present invention will discern whether a message is a supervision type by counting the number of repeats of a received message before deciding whether or not to perform the RSSI analysis.
  • the processing circuitry and software is provided with further intelligence in order to determine which supervision messages are to undergo testing and/or analysis in accordance with the present invention. This may be accomplished by designating a flag bit in the message as a test/no-test bit, wherein a logic true indicates that the transmission margin be tested, and a logic false indicates that the test need not be done.
  • the processor may implement a look-up table programmed with the identity of each device which is to undergo the transmission margin test, and thus utilize the device identification code to access the table and process the message accordingly.
  • the preferred embodiment has been described in conjunction with a wireless RF system, the invention can be easily applied to traditional wired systems such as local area networks (LANs) and the like, wherein it may be necessary or desired to test the margin of operation between the transmitter and receiver functions.
  • LANs local area networks

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Claims (31)

  1. Station réceptrice (6 ; 6a ; 6b) pour une utilisation dans un système de communication, station réceptrice qui comprend des moyens de réception (20 ; 20a) pour recevoir des signaux à partir d'une station émettrice distante, la station réceptrice pouvant fonctionner pour déterminer s'il existe ou pas une marge de puissance effective concernant la réception de signaux ;
       caractérisée par des moyens de commande (30, 32 ; 38, 42a ; 38b, 42a) qui peuvent déterminer si un signal reçu provenant de ladite station émettrice distante est de type de surveillance ou de non surveillance, et qui réalise un essai en réponse à l'identification d'un signal de surveillance pour déterminer si un signal de non surveillance provenant de cette station émettrice distante aura ou non la marge de puissance effective sur ledit signal de surveillance.
  2. Station réceptrice selon la revendication 1, consistant de plus à modifier un moyen (30) pouvant être commandé par lesdits moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) pour modifier un paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) en tant que partie dudit essai.
  3. Station réceptrice selon la revendication 2, dans laquelle, lors d'une réception par lesdits moyens récepteurs (20 ; 20a) d'un signal de surveillance ultérieur provenant de ladite station émettrice distante, ledit essai est réussi et lesdits moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) renvoient le paramètre fonctionnel de la station réceptrice (6 ; 6a ; 6b) à normal et font passer ledit signal de surveillance au traitement suivant.
  4. Station réceptrice selon la revendication 2 ou 3, dans laquelle le paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) reste modifié par lesdits moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) lors d'une réception par lesdits moyens récepteurs (20 ; 20a) d'un signal de surveillance provenant d'une station d'émission distante différente.
  5. Station réceptrice selon la revendication 4, dans laquelle lesdits moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) déterminent l'essai comme réussi pour la station émettrice distante différente lorsque le signal de surveillance provenant de cette station a été reçu avec succès alors que le paramètre opérationnel a été modifié, et en le faisant passer au traitement suivant.
  6. Station réceptrice selon la revendication 2, 3, 4 ou 5, dans laquelle lesdits moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) renvoient le paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) à normal si un autre signal de surveillance provenant de ladite station émettrice distante n'est pas reçu par lesdits moyens récepteurs (20 ; 20a) pendant une période de temps prédéterminée depuis la réception dudit signal de surveillance, la période de temps étant telle qu'au moins une partie d'un signal de non surveillance peut être reçu alors que le paramètre fonctionnel n'est pas modifié.
  7. Station réceptrice selon l'une quelconque des revendications 2 à 6, dans laquelle les moyens de commande (30, 32 ; 38a, 42a ; 38b, 42a) comprennent un sous-programme de surveillance pour contrôler le type de signal déterminé par les moyens de commande et pour commander le paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) en réponse audit type.
  8. Station réceptrice selon l'une quelconque des revendications 2 à 7, dans laquelle une modification du paramètre fonctionnel se fait en inhibant la sensibilité de ladite station réceptrice (6 ; 6a ; 6b), par exemple, en réduisant la sensibilité du signal d'entrée.
  9. Système de communication comprenant une station réceptrice (6 ; 6a ; 6b) selon l'une quelconque des revendications 1 à 8 et une pluralité de stations émettrices distantes (4), dont chacune comprend un moyen émetteur pour émettre des signaux de surveillance et des signaux de non surveillance.
  10. Système de communication selon la revendication 9, dans lequel ledit signal de surveillance et ledit signal de surveillance suivant sont corrélés l'un à l'autre.
  11. Système de communication selon la revendication 9, dans lequel ledit signal de surveillance et ledit signal de surveillance suivant sont identiques.
  12. Station réceptrice (6a) selon la revendication 1, comprenant de plus pour une utilisation dans ledit essai, des moyens (38a, 42a) pour traiter un signal électrique de sortie représentatif dudit signal de surveillance à un premier niveau de sensibilité et à un deuxième niveau de sensibilité inférieur audit premier à des fins comparatives ultérieures, une différence entre lesdits premier et deuxième niveaux de sensibilité étant représentative de ladite marge de puissance effective.
  13. Station réceptrice selon la revendication 11, comprenant de plus, à des fins comparatives ultérieures, un moyen (42a) pour déterminer si ledit signal électrique de sortie est sensiblement identique ou corrélé auxdits premier et deuxième niveaux de sensibilité, une identité ou une corrélation importante mettant en évidence l'existence de ladite marge de puissance effective.
  14. Station réceptrice selon la revendication 1, comprenant de plus un moyen (38b) pour mesurer la force du signal de surveillance reçu par ledit moyen récepteur et pour comparer ladite force avec un seuil prédéterminé, ledit seuil prédéterminé étant représentatif de ladite marge de puissance effective.
  15. Système de communication comprenant une station réceptrice (6b) selon la revendication 12, 13 ou 14, et une pluralité de stations émettrices distantes (4), dont chacune comprend des moyens d'émission pour émettre des signaux de surveillance et des signaux de non surveillance.
  16. Système d'alarme (2) comprenant un système de communication selon l'une quelconque des revendications 9 à 11 ou selon la revendication 15, dans lequel chaque station émettrice distante (4) de ladite pluralité de stations émettrices distante comprend de plus un détecteur d'alarme respectif, la disposition étant telle que, pendant l'utilisation, chaque émetteur distant émet un signal de non surveillance après réception d'un signal provenant de son détecteur d'alarme respectif, ladite station réceptrice étant sensible audit signal de non surveillance afin de déclencher une alarme, et dans lequel chaque station émettrice distante émet un signal de surveillance périodiquement pour amorcer ledit essai en vue de fournir un contrôle de ladite marge de puissance effective pendant un certain temps.
  17. Procédé pour vérifier une marge de puissance effective dans un système de communication comprenant une station réceptrice (6 ; 6a ; 6b) ayant un moyen récepteur pour recevoir des signaux de type de surveillance et de non surveillance provenant d'au moins une station émettrice distante (4), procédé qui comprend les étapes consistant à :
    (1) recevoir un signal de ladite station émettrice distante (4) ;
    (2) déterminer si ledit signal est de type de surveillance ou de non surveillance ; et
    (3) réaliser, quand ledit signal est de type de surveillance, un essai pour déterminer si un signal de non surveillance provenant de cette station émettrice distante (4) aura ou non la marge de puissance effective par rapport audit signal de surveillance.
  18. Procédé selon la revendication 17, comprenant de plus l'étape consistant à émettre un signal de surveillance périodiquement afin d'amorcer ledit essai pour contrôler ladite marge de sécurité de puissance du signal en fonction du temps.
  19. Procédé selon la revendication 17 ou 18, dans lequel ledit essai comprend les étapes consistant à modifier un paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) par une quantité représentative de ladite marge de puissance effective, et attendre la réception d'un signal de surveillance ultérieur provenant de cette station émettrice distante (4) tout en modifiant le paramètre fonctionnel.
  20. Procédé selon la revendication 19, comprenant de plus l'étape consistant à renvoyer le paramètre fonctionnel de ladite station réceptrice (6 ; 6a ; 6b) à normal si ledit signal de surveillance suivant provient de la même station émettrice distante que ledit signal de surveillance.
  21. Procédé selon la revendication 20, comprenant de plus l'étape consistant à maintenir le paramètre fonctionnel modifié quand un signal de surveillance est reçu à partir d'une station émettrice distante différente.
  22. Procédé selon la revendication 21, comprenant de plus les étapes déterminant l'essai réussi concernant la station émettrice distante différente lorsque le signal de surveillance provenant de cette station a été reçu avec succès alors que le paramètre fonctionnel a été modifié, et le faisant passer au traitement suivant.
  23. Procédé selon la revendication 19, 20, 21 ou 22, comprenant de plus les étapes consistant à :
    (a) mesurer une période de temps prédéterminée à partir de la réception dudit signal de surveillance ; et
    (b) renvoyer le paramètre fonctionnel de ladite station réceptrice à normal à la fin de ladite période de temps prédéterminée si aucun signal de surveillance suivant n'est reçu provenant de cette station émettrice distante, la période de temps prédéterminée étant telle qu'au moins une partie d'un signal de non surveillance peut être reçue alors que le paramètre fonctionnel n'est pas modifié.
  24. Procédé selon l'une quelconque des revendications 17 à 23, dans lequel l'étape consistant à modifier le paramètre fonctionnel comprend l'étape consistant à inhiber la sensibilité de la station réceptrice (6), par exemple en réduisant la sensibilité du signal d'entrée.
  25. Procédé selon la revendication 17, dans lequel ledit essai comprend les étapes consistant à traiter un signal électrique de sortie représentatif dudit signal de surveillance à un premier niveau de sensibilité et à un deuxième niveau de sensibilité inférieur audit premier à des fins de comparaison ultérieures, une différence entre lesdits premier et deuxième niveaux de sensibilité étant représentative de ladite marge de puissance effective.
  26. Procédé selon la revendication 25, comprenant de plus l'étape consistant à déterminer si ledit signal électrique de sortie est sensiblement identique ou corrélé auxdits premier et deuxième niveaux de sensibilité, une identité ou une corrélation sensible mettant en évidence l'existence de ladite marge de puissance effective.
  27. Procédé selon la revendication 26, comprenant de plus l'étape consistant à rejeter ledit signal quand une identité ou corrélation sensible n'est pas établie.
  28. Procédé selon la revendication 17, dans lequel ledit essai comprend les étapes consistant à mesurer la force du signal de surveillance reçu par ledit moyen récepteur, et comparer ladite force avec un seuil prédéterminé, ledit seuil prédéterminé étant représentatif de ladite marge de puissance effective.
  29. Procédé selon la revendication 28, comprenant de plus les étapes consistant à rejeter ledit signal de surveillance comme non reçu de façon valide quand ladite force est inférieure audit seuil prédéterminé, et fournir un signal de sortie pour indiquer que ledit essai n'a pas été réussi par cette station émettrice distante.
  30. Procédé selon l'une quelconque des revendications 17 à 29, comprenant de plus l'étape consistant à accepter tous les signaux de non surveillance et à les faire passer au traitement suivant.
  31. Procédé selon l'une quelconque des revendications 17 à 30, comprenant de plus l'étape consistant à émettre lesdits signaux de surveillance et de non surveillance par radiodiffusion avec des ondes électromagnétiques entre ladite station émettrice distante et ledit récepteur.
EP19970201449 1996-05-20 1997-05-20 Système d'alarme automatique avec analyse d'un signal de surveillance Expired - Lifetime EP0814445B1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US650292 1991-02-04
US08/650,292 US5828300A (en) 1996-05-20 1996-05-20 Alarm system with supervision controlled receiver parameter modification
US08/685,716 US5748079A (en) 1996-05-20 1996-07-24 Alarm communications system with independent supervision signal analysis
US685716 1996-07-24
US08/685,539 US5801626A (en) 1996-05-20 1996-07-24 Alarm communications system with supervision signal RSSI analysis
US685539 1996-07-24

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EP0814445A2 EP0814445A2 (fr) 1997-12-29
EP0814445A3 EP0814445A3 (fr) 1999-04-14
EP0814445B1 true EP0814445B1 (fr) 2003-12-17

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ITTO20070082A1 (it) * 2007-02-05 2008-08-06 Elkron Spa Metodo e sistema per valutare la qualita' di collegamento radio tra due dispositivi di tipo wireless

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US4754261A (en) * 1987-03-30 1988-06-28 Pittway Corporation Security system
DE4024821A1 (de) * 1990-08-04 1992-02-06 Koettgen Gmbh & Co Kg Kleinsender-kontrolle
DE4035070A1 (de) * 1990-11-05 1992-05-07 Norbert Schaaf Funkalarmanlage

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EP0814445A3 (fr) 1999-04-14
EP0814445A2 (fr) 1997-12-29
DE69726793D1 (de) 2004-01-29
DE69726793T2 (de) 2004-06-17
ES2208814T3 (es) 2004-06-16

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