Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
  • H04M11/002—Telephonic communication systems specially adapted for combination with other electrical systems with telemetering systems

Definitions

• This invention relates to systems for utilizing telephone networks to provide additional functions, beyond those of traditional telephone service involving conversations between subscribers. More particularly, the invention relates to such systems in which the network is additionally used to monitor the conditions of one or more instrumentalities, located at the subscriber's premises.
• the instrumentalities in question may be of various types.
• One type is a device for providing an electrical alarm signal when an abnormal condition is detected at the subscriber's premises.
• Such an abnormal condition may be a fire, an unauthorized entry, a malfunction of some machinery under surveillance, etc.
• Another type may be a device. which provides an electrical signal indicative of the state of some equipment at the subscriber's premises, even though there is no abnormality. This could be utility meter readings, eteorolgical measurements, operational data of process equipment, etc. Still other types can be envisioned.
• ackground Art 2-
• the present invention is by no means the first to deal with, systems of this kind. Indeed, numerous such systems have previously been proposed. However, so far as the present inventors are informed, all such previously proposed systems had characteristics which detracted from their usefulness, or their desirability, in one way or another.
• STU subscriber terminal unit
• each STU there are connected the various instrumentalities which are to be monitored by the system, so that their output signals are available in electrical form within the STU.
• the scanner interrogates the STUs at appropriate times by means of audible signals within the audible range.
• the STUs reply by means of similar signals to indicate the status of the instrumentalities at the respective subscriber premises.
• a special signal at a frequency well below the audible range is also produced at the STU, and is transmitted to the scanner over the telephone loop, which of course also carries the other conventional telephone signals: voice, dial tone, ringing, busy tone, etc.
• This special signal (hereafter called "low tone”) is prefer €bly present continuously, during both on- and off-hook conditions, but only if all the instrumentalities at the particular subscriber premises are within their predetermined normal, or safe, range of states.
• the scanner normally interrogates the individual STUs n a predetermined, cyclical sequence.
• other deviations from that sequence are preferably also provided.
• a particular STU is first activated as part of the system, it is preferably interrogated immediately, even though th s nay -6- be out of its normal sequence, to determine the status of ts associated instrumentalities without delay.
• the STU at that location is preferably immediately interrogated, even though low tone had not indicated a danger or alarm condition.
• the low tone signal is the initial source of information concerning the states of the instrumentalities at a STU.
• the scanner monitors the presence or absence of the low tone signal during both on-hook and off-hook conditions of the telephone. Only after the low tone signal is lost indicating a change in state of at least one instrumentality, does the scanner interrogate the corresponding STU to determine the reason for the loss of the low tone signal.
• Figure 1 is an over-all system block diagram of an embodiment of the invention
• Figure 2 is a block diagram of a scanner forming poart of the embodiment of Figure 1;
• FIG 3 is a block diagram of a subscriber terminal unit (or STU) forming part of the embodiment of Figure 1.
• this shows a telephone network 10 which, in itself, is entirely conventional in all respects. Indeed it is one of the features of the present invention that it can be practiced using a conventional telephone network, without interfering with its operation in the slightest.
• This network 10 which is shown in highly simplified form in Figure 1, includes a plurality of subscriber telephone handsets, respectively designated by reference numerals 11, 12 and 13. Each of these handsets is connected to its own local telephone line, or loop. These are respectively designated byreference numerals 14, 15 and 16. These local lines, in turn, all lead to a switching system 17, normally located at the telephone central office. All of these elements of the system may take essentially any conventional form.
• the subscriber handsets 11, 12, 13 may be of the dial or pushbutton variety.
• the central office switch 17 may be of the rotary, or cross-bar r or even fully electronic variety.
• the local lines 14, 15, 16 may also be of any conventional variety, including repeaters, equalizers, etc., as appropriate, provided only they are capable of passing the low tone signals.
• the system of Figure 1 further includes a scanner 18.
• This scanner is prefrably physically located at some point at which it can conveniently be connected to the various individual subscriber lines. This may be at the central office, where the switching equipment 17 is also located.
• connections 19, 20 and 21 are shown between the scanner 18 and the respective lines 14, 15 and 16.
• STU subscriber terminal unit
• x ⁇ hich shows the "innards" of the scanner 18, these include first, second and third multiplexers 25, 26 and 27. These are all time-division multiplexers which, in conventional manner, select the signals on different ones of connections 19, 20 and 21 at different times, and transmit the so-selected signals to their respective outputs.
• multiplexer 25 is a two-way device, which is also capable of distributing selectively, at different times, to the different connections 19, 20 and 21, signals supplied to the other "end” of this multiplexer 25. Thus, either end of multiplexer 25 can serve as input and output, as appropriate.
• the multiplexer 25 is connected to a transmit- receive switch 28 (also abbreviated as T/R switch).
• T/R switch 28 which operates in the receive mode in turn supplies signals from multiplexer 25 to demodulator 29 for equency-shift keyed (abbreviated as FSK) signals.
• the portion of T/R switch 28 which operates in the transmit mode receives its input signal (to be transmitted) from a modulator 30 for FSK signals.
• demodulator 29 supplies its output signals to system controller 31, and modulator 30 receives its input signals form the same controller 31.
• multiplexers 26 and 27 supply their respective output signals to different filters 32, 33.
• filter 32 supplies its output signals to detector 34, while filter 33 supplies its output signals to detector 35. Both of these detectors ultimately supply their output signals to the same system controller 31 which was previously mentioned.
• This STU 22 ( Figure 3) is connected to line 14, which also connects subscriber handset 11 to the network switch 17 and to scanner 18.
• Signals received from line 14 are supplied within STU 22 to a filter 36, the output signal from that filter being supplied to a demodulator 37 for f equency-shift keyed signals.
• the output signals from demodulator 37 are supplied to signal processing circuitry 40.
• Signal sources 41, 42 and 43 in Figure 3 represent electrical signal outputs from corresponding instrumentalities (not shown) which are located at the same premises as the STU 22 and handset 11, and which are intended to be under the surveillance of that system which embodies the present invention.
• signal source 41 may be a relay which closes and thereby establishes an electrical signal path whenever a fire alarm device at the subscriber's premises senses an alarm condition.
• signal source 42 may be a relay which operates similarly when a burglar alarm is activated, and signal source 43 may function similarly in case of interruptions in a temperature control system.
• the two carrier frequencies used are preferably in the vicinity of 2,700 and 2,900 Hz, i.e. near the upper end of the band of frequencies passed by a typical local telephone line.
• multiplexer 25 supplies that train to connection 19, whence it reaches STU 22 via telephone line 14. Note that the same signal train also reaches handset 11 via line 14. More will be said about this later .
• the signal train described above is demodulated in FSK demodulator 37, after passage through filter 36, which is preferably a band-pass filter constructed to selectively transmit the band of frequencies occupied by the two FSK carrier frequencies (e.g. the 2,700 to 2,900 Hz band).
• filter 36 which is preferably a band-pass filter constructed to selectively transmit the band of frequencies occupied by the two FSK carrier frequencies (e.g. the 2,700 to 2,900 Hz band).
• filter 36 which is preferably a band-pass filter constructed to selectively transmit the band of frequencies occupied by the two FSK carrier frequencies (e.g. the 2,700 to 2,900 Hz band).
• This processor 40 is so constructed as to respond to the above-mentioned signals to generate a train of modulating signals which are in turn supplied to FSK modulator 38, where they produce a corresponding train of FSK-modulated signals, preferably at the same carrier frequencies as those received from scanner 18.
• This train of FSK-modulated signals returns to that scanner via line 14 and connection 19. In passing, it is noted that this response signal tram of course also reaches handset 11.
• the multiplexer 25 is activated by controller 31 in time coordination with the expected arrival of this responsive signal tra from STU 22 so as to pass signals on connection 19 to the FSK demodulator 29, via the receive portion of T/R switch 28.
• Demodulator 29 recovers the signals which had been used to modulate the FSK signals at the STU 22 and supplies same to system controller 31.
• the modulating signals produced by signal processor 40 provide information about the state of the signal sources 41, 42 and 43. For example, if at STU 22 there are present no relay closures denoting alarm states of the various instrumentalities under surveillance," then one predetermined pattern of modulating signals is produced by processor 40. If one or more relay closures are present, then correspondingly different patterns are produced, and the (demodulated) signals which ultimately reach the controller 31 from STU 22 are also different.
• the system controller 31 responds to the paricular pattern of signals received in a particular way. For example, if a pattern of signals is received which indicates that there is an alarm state at signal source 41 of STU 22 ( Figure 3), the system controller 31 provides a corresponding alarm signal to any desired indicator.
• this may be an indicator at the fire department which is in charge of the subscriber's premises at which the STU 22 is located.
• Such uses of the signal pattern received from each STU are conventional, in themselves, and may take any of numerous forms, without affecting those aspects of the overall system which constitute the present invention. The means for accomplishing these uses are therefore not further described or illustrated herein.
• the generator 39 which is provided at each STU ( Figure 1)
• this generator 39 is constructed so as to produce a signal at a frequency substantially below the audible frequency range.
• this generator 39 may be capable of producing a signal of approximately 25Hz frequency. It is because of its operation at such a low frequency that generator 39 is referred to as a
• the generator 39 does not operate continuously. Rather it is controlled by signal processor 40 so as to be in one or the other of two states. So long as the signal sources 41, 42 and 43 are all in their non-alarm state, the signal processor 40 causes the low tone generator 39 to produce its low frequency output signal, which thereupon reaches the scanner 13 via telephone line 14 and connection 19. In contrast, whenever any one or more of signal sources 41, 42 or 43 is in an alarm state, then signal processor 40 causes the low tone generator 39 to stop producing its low frequency output signal. This low frequency signal therefore also ceases to reach scanner 18.
• each STU is equipped m substantially similar manner as the STU 22 which is shown specifically m Figure 3, and operates in substantially the sane way. *
• multiplexers 26 and 27 are energized by system controller 31 so as to sequentially samplethe signals appearing on connections 19, 20 and 21, respectively.
• a signal representing, in recurrent sequence, the hook condition of the different handsets 11, 12 and 13 is derived via filter 32 and hook detector 34, and supplied to system controller 31.
• a signal representing, also recurrent sequence, the presence or absence of the low frequency signals from the different low tone generators of STUs 22, 23 and 24 is derived via filter 33, and supplied to system controller 31.
• a second possible situation is that the telephone handset 11 is still on-hook, but an alarm condition prevails at STU 22.
• the on-hook condition is still sensed at scanner 18 and the output from FSK modulator 30 is still supplied periodically to that STU 22.
• the STU now responds with an alarm signal from its FSK modulator 38. This is detected by FSK demodulator 29, and system controller 31 takes the appropriate alarm action, as previously described.
• a third situation is that the telephone handset 11 is * off-hook, and that there is no alarm condition at STU 22.
• This off-hook condition is now sensed at scanner 18, which thereupon does not supply output signals from FSK modulator 30 to STU 22 for the duration of this third situation, provided the scanner 18 also senses a low tone signal received from the same STU. It will be recalled that a low tone from generator 39 is produced when no alarm condition prevails.
• the fourth situation is that the telephone handset 11 is again off-hook, but that there is at least one alarm condition at STU 22.
• the off-hook condition at STU 22 is again sensed at scanner 18, but so is the absence of the low tone signal from that same STU.
• the scanner 18 does supply output signals from FSK modulator 30 to STU 22, of the same type as it would have supplied had the handset 11 been on-hook, rather than off-hook. This will, of course, cause a reply from STU 22, in the form of FSK modulated signals from its modulator 38, which will in turn be detected at scanner 18, and used to produce the desired alarm response.
• a particularly "happy" combination of interacting features is believed to be provided by relying primarily upon the high-frequency end of the audible range for on-hook alarm reporting purposes, while relying upon a sub-audible signal for initial off-hook alarm reporting purposes.
• Use of the high-frequency end makes a relatively high data rate possible, which means that relatively detailed information about the instrumentalities under surveillance can be obtained, and also that this can be repeated frequently, and relatively many STUs can be accommodated by the system.
• Use of the sub-audio end makes it possible to speak without inter ⁇ ference during the (presumably overwhelming) majority of the times when no alarm is present. Yet, by shifting from sub-audio to high frequency, the desired detailed information can be obtained when needed, i.e. when an alarm condition arises, even during off-hook perlods.
• low tone provides redundancy for the alarm function of the system during on-hook conditions. During that condition, low tone continues to be transmitted from each STU to the scanner, so long as no alarm is present at the STU. Any low tone interruption during on-hook conditions is also sensed by the scanner, and provides what might be called a "coarse" back-up alarm indication for the more detailed one which is normally provided by the FSK-modulated reply from the STU.
• the alarm indication during off-hook periods is fail-safe, since it is the disappearance of the low tone signal which indicates an alarm condition.
• failure of equipment in the STU will cause a pseudo-alarm indication conducive to prompt correction.
• the hook status is detected for each STU at the scanner 18.
• the STU at that subscriber's premises is preferably made the next one to receive the
• Another highly desirable feature of the invention is that the individual components of the overall system can take any one of a number of known forms.
• the multiplexers 25, 26 and 27 may be of known construction.
• the filters 32 and 33 may be of known form, - suitable for selecting the particular frequencies desired to be passed on to the hook detector 34 and low tone detector 35, respectively. These detectors, themselves, may also be of known form, the hook detector 34 being a conventional part of telephone systems, and the low tone detector 35 being a detector of the presence of absence of the 25 Hz low tone signal.
• the T/R switch 28 may be of known forms, and the system controller 31 may include any known circuitry capable of providing the straightforward sensing and responsive control functions which have been described.
• system controller 31 may comprise a conventional source of timing signals, from which are derived the sequential operating signals for the multiplexers 25, 26 and 27.
• Also driven by signals derived from the timing signals may be sources, such as shift registers, of the trams of modulating signals for FSK modulator 30.
• AND gate circuitry may be used to -detect the simultaneous presence of off-hook detected signals and low tone detected signals. Such detection is used by conventional circuitry to inhibit signals to the FSK modulator 30.
• the FSK demodulator 37 and the FSK modulator 38 may again be of any known form, as also the filter 36 which precedes the demcfdulator 37.
• the low tone generator may also be of any known form capable of producing the desired 25 Hz signals when energized.
• the signal sources may be simple relay circuits operated by the respective alarms, and the signal processor may be any known form of digital logic, or of microprocessor circuitry programmed in conventional manner to elicit the appropriate timed signal responses, as previously described.
• the telephone system itself is completely unaffected by the invention. No added filtering is required in the telephone system; particular there is no leakage of low tone signals from one side of the network switch 17 to the other because the network switch contains adequate filtering for other reasons, namely to isolate different levels of DC on opposite sides of the switch.
• low tone may be used to indicate that all the measuring instruments are continuing to work, even while the telephone handset is off-hook.
• STU can then supply the more detailed data desired concerning the equipment.
• the system illustrated in Figures 1, 2, and 3 can be operated in a second way.
• scanner 18 can be arranged to sense the presence or absence of the low tone signals and only upon loss of the low tone signal from a particular STU interrogate that STU to determine the reason for the loss of the low tone signal.
• the low tone signals provide the initial indications of the states of the instrumentalities. So long as the low tone signal is being received by the scanner from a particular STU, the scanner does not interrogate that STU because the presence of the low tone signal is an indication that the STU need not be interrogated (i.e. all the instrumentalities connected to the STU are m a "no alarm" condition).
• the scanner senses a change and transmits interrogation signals to the particular STU to determine the reason for the loss of the low tone signal, which is indicated by the response signals transmitted from the STU.

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Alarm Systems (AREA)
• Telephonic Communication Services (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Gyroscopes (AREA)

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• 1985
  • 1985-03-12 NL NL8520059A patent/NL192419C/nl not_active IP Right Cessation
  • 1985-03-12 DE DE3590106A patent/DE3590106C2/de not_active Expired - Lifetime
  • 1985-03-12 AU AU40699/85A patent/AU573323B2/en not_active Expired
  • 1985-03-12 JP JP60501298A patent/JPS61502021A/ja active Granted
  • 1985-03-12 EP EP19850901736 patent/EP0177554A4/en not_active Ceased
  • 1985-03-12 WO PCT/US1985/000406 patent/WO1985004302A1/en not_active Application Discontinuation
  • 1985-03-12 BR BR8505861A patent/BR8505861A/pt not_active IP Right Cessation
  • 1985-03-12 GB GB08527702A patent/GB2167625B/en not_active Expired
  • 1985-03-12 CH CH4959/85A patent/CH672040A5/de not_active IP Right Cessation
  • 1985-03-12 DE DE19853590106 patent/DE3590106T/de active Pending
  • 1985-03-13 CA CA000476340A patent/CA1230692A/en not_active Expired
  • 1985-03-15 NZ NZ211461A patent/NZ211461A/xx unknown
  • 1985-11-14 SE SE8505399A patent/SE462667B/sv not_active IP Right Cessation
  • 1985-11-15 NO NO854558A patent/NO854558L/no unknown

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