CA1230692A - Remote subscriber interaction system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:
A central control unit (scanner) is connected across a set of subscriber loops. At each subscriber's premises, an individual subscriber terminal unit (STU) is connected across that particular subscribers loop. To each STU are connected the various instrumentalities which are to be monitored by the system, e.g. fire alarms, burglar alarms, etc. A signal below the audible range (low tone) is produced at the STU, and transmitted to the scanner over the telephone loop if, but only if, all the instrumentalities at the particular subscriber premises are in a given state (e.g. non-alarm). If not, low tone is stopped. Such stoppage is sensed by the scanner, and causes immediate transmission of FSK modulated signals in the upper part of the audible range from the scanner to the corresponding STU, whether the associated telephone is on-hook or off-hook at the time. The reply from the STU to such transmission provides information about the reason for the stoppage, i.e. what is the source of the alarm.

Description

~2~6~2 9375-19 Technical Field 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 unauth-prized 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 sub-scriber's premises, even though there is no abnormality. This could be utility meter readings meteorological measurements, operational data of process equipment, etc. Still other types can be envisioned.

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aquiline art The resent invention is by no means the first to deal with systems of this kind. Indeed, numerous such systems have previously been proposed. T~owevel, so jar as the present inventors are informed, all such previously proposed systems had characteristics itch retracted from Neil usefulness, or their desirability, in one way OX another Fox example sore pLioL systems proposals involved the use of auxiliary signals which are audible to the subscriber when using the tel~nhone for conventional conversational purposes. This is not only disturbing to the subscriber, but also contravenes the technical reselections impose by some telephone companies, or governmental agencies.
Owner such prior system proposals involved the use of auxiliary signals which were above the range of Adele C~equencies. Tlot~eveL, this createf1 electrical filteLlng requirements within the system itself, and possibly also within the conventional telephone network, ah were difficult to implement, and also costly, to the point of impaling the economic acceptability of the system Still other system proposals, in an effort to overcome drawbacks such as Natalie avow, simply sacLlflce~ sore desirable system junctions, such as reliable surveillance of the e~uipl~ent at the sul~scLiber's premises, or the like.

closure of the Invention -ccordin-~ly, it is a principal object of the resent invention to provide a system which cooperates with a conventional telephone Natalie to pLoVi~3e add~tlorlal Elections, but in an lmploved manner as compiled with previously proposed systems lnten'le-l fox the salve ~eneLal purpose.
It is another object of the pLesei1t invention to pLOVl'.3e such a system '~hlcll lacks one OX more of the shortcomings of previously proposed systems.

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It is another object to provide such a system which does not use auxiliary sunless that ale audible to the subscriber US in nodal telephone usages.
It is another object to pLovlde a system which does not rely on signals above the audible frequency Lange.
It is another object to pLovlde a system which does not Lyle sr~eclal electrical fllteLing within the conventional telephone netlike It is another object to privily a system which provides a high degree of Reliable surveillance of the equi~ent at the subscLibeL's premises.
These and other objects which will appear are accomplishes in accoL3ance with the present invention as follows.
t a point at which a group Ox subscriber loots to be served by the system is conveniently accessible, a central control into (herelnafteL caller "scanner") is connected across all these subscriber loops. At each subscLibeL's premises, an individual electronic unit hereinafter Cole ~suhscLlber terminal unit or "STY") is connecter across that particular subscribes loon.
To each STY there are connecter the callous instrumentalities which aloe to be monitored by the system, so that their output sl~nal.s are ava~la'~l2 on electrical old within the Starr.
In one mode, the scanner inte~Logates the s~rlJs at appLopLiate times by means of audible signals within the Abel Lane. The Storages Lapel by eons of sim1laL signals to indicate the status of the lnst~umentalitles at the respective sul~scLiber Demises Thus noLrlal ~atLeLn of lnterLoqatlon Ann Lapel is limited to periods ruling icily the subscLibeL's telephone is on-hook, i.e., en the subsc~ibeL lo not using the telephone for conventional purposes, and ceases when the subscriber picks us the telephone Lowe. klutz an oEE--'nook connation.

A special signal at a frequency well below the audible range is also produced at the STUN and is transmitted to the scanner over the telephone loop which of course also carries the other conventional telephone signals: voice, dial tone fining busy tone, etc. This special signal (heLeaEteL called slow tone") is preferably present continuously, during both on-and okay conditions, but only it all the instrumentalities at the ~aLticulaL subscribe premises are within their pLedeteLmlned nodal or safe, range of states.
If any one or more of these instrumentalities desalt iron that Lange, lye., assumes a state of ranger OX alarm, production of low tone within the Stir lo discontinued. Such continuance of low tone is sensed by the scanner, and causes immediate interfusion of the particular STY which is the souse of Tunis Plleno~enon, even though the associated telephone is off-hook, so that this STY would normally not be interrogatefl (or reply) at this time. The reply to such interrogation which is then produced by the STY provides in~orrnatlon about the reason for the observed phenomenon, i.e.
what is the source ox the danger or alarm.
s previously noted, inteLLogatlon and Reply take place within the audible frequency Lange, and are therefore supplies on any other use of the telephone 311L lnq the off-hook condition, e.g. upon subscribe conversations.
Louvre, this OCCllLS only in response to a dangle OX alarm indication. TheLefoLe, it is not considered objectionable, nor it it prohibited by telephone ref3ulatlons. Indeed, it actually has the desirable aspect of simultaneously alerting the tele~hol-e user to the s1tllation In the absence of a phenomenon such as described above, the scanner normally lnteL~OgateS the lndlv~dual Stun in a predeterlninedt cyclical sequence. However, other datelines eon that cellulose are preferably also provided. Fox example, when a particular STIR lo first activatec3 as pelt of the system, it is l-LeEeLat)ly inteLLoga~.efl lr~lnedlat:ely, even though this ray be out ox its normal sequence, to determine the status of lots associated instrumentalities without delay. Also, whenever a subscriber hangs up, the Storage at that location lo preferably immediately interrogated, even though low tone had not indicated a dangle OX alarm condition.
In another mode, the low tone signal is the initial source of ~nEoLmation concerning the states of the instrumentalities at a STUN Instead of starting with the transmission of interlocution sunless and the Reception of responses, the scanner monitors the presence or absence of the low tone signal during both on-hook and ofE-hook conditions of the telephone. only after the low tone signal is lost indicating a change in state of it least one 1nstrumentallty, does the scanner interrogate the corresponding STY to determine the Lesson or the loss of the low tone signal.

Brie ~escriDtion of Drawings For Luther details, reference is made to the discussion which follows, in light of the accompanying drawings wherein:
Figure 1 is an over-all system block diagram of an embodiment of the invention;
Figure is a block diagram of a scanner forming port of the embodiment of Phyla 1; and Figure 3 is a block diagram of a subscribe terminal unit (or Jo forming part of the embodiment of Figure 1.
The same reverence nu~eLals designate similar elements in the defoliant figures.

Best lode of CaLrinq jut the Invention Rerolling to Flyer 1, this shows a telephone network in which, in itself, is entirely convolutional in all Respects Indeed it it one of the features of the present invention that ~L2~9;~

it can lye practiced using a conventional telephone network, -without inteLfeLing with its operation in the slightest.
his network I which lo shown in highly simplified form in Figure 1, includes a pluLallty of subscribe telephone handsets, respectively designated by reference numerals 11, 12 and 13. Each of these handsets is connected to its own local telephone line, or loo. These are respectively designated by reference numerals 14, 15 and 16. These local lines, in turn, all lead to a s~ltchin~ system 17, normally located at the telephone central office. ~11 of these elements of the system Jay take essentially any conventional form. The subscriber handsets 11, 12, 13 may be of the dial or pushbutton Volt Toe central office Sl~1itC)l 17 may be OX the rotary, or crossbar or even fully electronic variety. The local lines I 15, I Jay also be of any conventional variety, including repeaters, equalizes, etc., as appropriate, provided only they are capable ox Passing the lo tone signals.
In accordance with the present invention, the system of Flyer 1 further includes a scanner 18. This scanner is preferably physically located at some point at which it can conveniently be connected to the various individual subsc~iher lines This Jay be at the central office, where the switching equi~ent 17 is also located. In figure 1, connections 19, 20 and 21 are shown between the scanner 18 and the respective lines 14, 15 and lit. Further in accordance with the present invention, at each individual subscribe location, there is provided a separate subscriber terminal unit, abbreviated as STUN respectively designated by reference numerals 22, 23 and attention is lnvite~3 to the fact that equipment for only three subscribes is shown Lo Pharaoh 1. IloweveL, it channeled be understood that this US only SOL simplicity of illustration. the invention is intended to be used with larger numteLs ox sociables in which case toe handsets, the connections and the Stacy Gould all be correspondingly increased 31 ;2~0~32 in nubilous. Tl-1s lo sy~bollcally indicated in Figure 1 by wide spaces bridged by broken lines, between all the foregoing elements of the overall system.
Turning now to Figure 2, 7hich shows the n innards" of the scanner 18, these include first, second and third l~ultiplexeLs US, I and 27. These ale all t1me-divislon multiplexes which, in conventional manner, select the signals on d1EEerent ones of connections 19, 20 and 21 at delineate tomes, and transmit the so-selected signals to their respective outputs. ~1OreoveL, Tnultlpl?xer 25 lo a two-way device, which is also capable of distributing selectively, at different toes to the different connections lo, 20 and 21, signals supplied to the other wend" of this multiplexer 25. Thus, either end of rnultlplexeL 25 can solve as input and output, as appropriate. The multiplexer 25 is connected to a transmit-receive switch I (also abhtev1ated us To switch). The portion of I switch 28 which operates in the receive Node in turn supplies signals LOWE Multiplexer 25 to demodulator 29 fox Ere-luency-shift keyed abbreviated as FISK) signals. The option of T/R switch ?.~ which operates in the tLansrnit mode receives its input signal (to be transmitted) Elm a modulator on fox I signals.
In turn, ~3ernoclulator 29 supplies its output signals to system controller 31, and modulator 30 Receives its input skinless Elm the same controller 31.
s for multiplexes 26 and 27, these supply their respective output signals to (Laurent EllteLs 32, 33. In turn, filter 32 supplies its output signals to detector 34, while flotilla 33 surplus its output signals to cletectoL 35.
Both of these detectors ultilnately supply their output signals to the semi? sister cnntrolleL 31 which was previously ~lentionecl.
Because of the inteLlockin~ relationship between the onerat1ons of the parlous elements of scanner 10 which are shown in Faker 2, and elements of each STY 22, 23 and 24 (see royalty 1), it is believed nauseously to ~escrlbe the latter in Lo Luther detail err dealing mole fully it the operational characteristics of either. To that end, reference is now made to Figure 3, which shows the "inlays" ox STY 22. It '~1l11 be understood that all Stacy Jay be substantially identical in construction so that the description ox STY 22 presenter herein Gould apply equally to Stun 23 and I and to any additional Sums symbolized by the dashed lines between STY 23 and STY 24 in Figure 1.
This Storage 22 (Figure 3) lo connected to line 14, which also connects subscriber handset 11 to the network switch 17 and to scanner 18.
Signals received prom line 14 are supplied within STY
I to a jilter 36, the output signal prom that filter being supplied to a demodulator 37 for frequency-shift keyed sunless.
supplied to line 14 are signals from a modulator 38 for ~Lequency-shift keyed signals.
Also supplied to line 14 are signals from a signal generator 39.
In turn, the output signals from ~e~odllator 37 are supplied to signal processing circuitry 40.
Signal sources 41, I and 43 in figure 3 represent electrical signal outputs from corresponding instrumentalities (not Chilean) high are located at the save promises as the STY
22 and handset 11, and which are intended to be under the surveillance of that system itch emhodles the present invention.
FOX example, signal source 41 nay be a relay which closes and thereby establishes an electrical signal path whenever a fire alarm device at the subscLlbeL's premises senses an alarm condition. By the seine token, signal source 42 may be a relay which operates slmilaLly when a burglar claim is activated, an signal source I may function similarly in case ox interruptions in a temperature control system.
Proceeding now to the operational characteristics of tune elements ~escribe~l above, it is easily to point out first that these lo what might be called a closed loop relationship between the scanner 18 and each STY 22, 23 and 24. That is, the scanner produces sl~nals hill are transmitted to the STUN
Nash responds thereto to transmit signals back to the scanner, an so on in back-anr3-foLth, or closed-loop relationship.
For description here, let us therefore initially break Into the close loop at that output from system controller 31 which is connected to FISK modulator 30 figure 2). This system controller is construcke~ so as to recurrently produce at that OlltpUt FISK modulating signals in a predetermined pattern. This pattern is such that the trudges 22, 23, 24 forming part OX the overall system respond to it to provide, in turn, certain output signals as descried herelna~teL The US modulator responds by produc1n~ an FS'K-modulated equivalent of the signals from controller 31. The two curlier wrinkles used are preferably in the vicinity of 2,700 and ~,900 Ho, i.e. Neal the upper end ox the hank of: fLequencles passed by a ty~lcal local telephone line.
hose FSX-modulate~ signals prom modulator 30 then sass through T/R switch 28 to mllltlplexer 25. There, control signals are also applied from system controller 31, in such time coordination with the signals from FISK modulator 30, that the latter- are channeled to one OX arlotheL of connections 19, I and 21, depending upon which one of Swiss 22, 23 or 24 lo the intended destination ox these sl~nals Roy I !no~ulatoL 30 at that time.
Assuming that the inten~e-l ~3estinatlon for a particular signal train is STY 221 then multiplexer 25 supplies that train to collection lo hence it roaches STY 22 via telephone line 14. Note that the save signal train also reaches handset if via line lo. Mole lull be said about t~lS
later .
on LeaCh~nC~ So 2'2, and Lowlier Lo no:- to June 3, tile sl~nal train descril~eA above is de~lodulat~c3 on US
~emo-llllatol: 37, betel ask thLouqh flyweight I which is

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PLefeLably a band-pass jilter constLucte~l to selectively transmit the band of frequencies occupied by the two FISK
carrier frequencies (e.g. the 2,7nn to 2,9n0 Ha band). it the OUtpllt of demo~ulatoL 37, there ale therefore reconstructed the modulatill~ signals oLlglnally pLovlded ho controller 31 (Figure 3). These reconstructed signals ale supplied to signal processor 40 within STY 22.
This pLoCeSSoL 40 lo SO constructed as to Respond to the above-mentioned signals to generate a train ox modulating signals which are in turn supplied to FSI~ modulator 38, where they produce a corresponding train of FSK-rnodUlated signals, prefeLahly at the same carries lunacies as those received from scanner 18. Russ train of FSIC-modulated signals returns to that scanner Viol line lo and connection 19. In passing, it is noted that this response signal train of course also reaches handset 11.
At the scanner, the rtultlplex~L I is activated by controller 31 in time coordination with the expected arrival of this responsive signal train from Stir 22 so as to pass signals on connection 19 to the FOX demodulator 29, via the receive portion of T/R switch ~.~. Det~odulatoL I recovers the signals which had been used to modulate the FISK signals at the STY 22 and supplies same to system controller 31.
Reverting now to STY 22 (Figure 3), the modulating signals produced ho signal processor 40 provide information about the state of the signal sources 41, 42 and 43. or example, if at Srrrl 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 Cole relay closures are resent, then correspondingly difEerellt patterns are produce-3, and the (demodtllated) signals which ultimately coach the controller 31 prom it 22 are also different The system controller 31 responds to the particular pattern of siqn.tls received in a ~aLticular way. For example, it a pattern of signals lo L received which indicates that these is an alarm state at signal source 41 of STY 22 (Figure 3), the system controller 31 provides a corresponding alarm signal to any desired indicator. For example, this may be an indicator at the Lowe department which is in charge of the subseriheL's promises at which the STIR 22 is located Such uses of the Snow Pattern received ELM each TAO are conventional, in themselves, and may take an of numerous foLrns, without a~feetin~ those aspects of the overall system which constitute the present invention. The means fox accomplishing these uses ale therefore not ~ULtheL described OX lllUStLated heroin.
attention is now again directed to the tact, previously neutral, that tune US signals passing back and forth between scanner I and any given STY also reach the telephone handset with which that truly is associated. Tnl~s is not a problem, so long as the telephone is on-hook, since these FISK psychoanalyze retain unnoticed by the subscriber during such on-hook conditions. iota so during of hook conditions. Tire US
signals are within the audible ELe~uency range. The there~oreare herald by the subseri`oer when trying to use the Tony for normal co~unlcatlon purposes. This is (lute disturbing, especially since these US signals are intentionally cause to recut at fluent intervals, in order to provide indications of the state of the instrulnentalltles under surveillance which are Relatively up-to-date. Moreover, even if the audible effect ox these FISK signals wile cons~deLed acceptable by the subscriber, they Walt still in many instances contravene telephone company Andy: governmental regulations, which pLoh~bit the intro-3uctlon ox such extraneous I.
audible signals into the network during off-hook conditions.
In accordance with the present invention, this Tl)atteL
is dealt with as follows.
rho qeneLatoL I which is provided at each STY (Flukier 3) lo constructed so as to produce a signal at a frequency su')st-lntLally below the Audi to luckiness Uncle Fox example, ~23~69~

this ~eneLatoL I may be capable of producing a sigllal of appLoxi~ately 25~z frequency. It is because of lots operation at such a low ~Leguenc~l that ~eneLatOr 39 lo referred to as a n low tone" generator.
The venerator 39 does not operate continuously.
Ethel it lo controlled by signal processor 40 so as to be in one or the other of two states. owe long as the signal sources 41, 42 and 43 are all in their non-alaL~ state, the signal ocessor 40 causes the low tone generator 39 to produce lots low frequency output siqn~l, which thereupon reaches the scanner 18 via telephone line 14 an connection 19. In contrast, whenever any one OX lore of signal sources 41, 42 or I is in an alarm state, then signal processor 40 causes the low tone generator 39 to stop prosing its low frequency output signal. this loll frequency signal Thor also ceases to reach scanner 18. us previously lnd1cated, each STY is equip in substantially similar cannel as the TAO 22 which is shown specifically in Figure 3, and operates in substantially the Salle Tao.
t that scanner 18, multir)lexers 26 and 27 are energized by system controller 31 so as to sequentially sa~plot~e SigllalS appeal lo on connections lo, 20 and Al, respectively.
FLOW mUltiploXeL oh, a signal -representing, in Recurrent sequence, the hook condition of the different handsets if, 12 and 13 is derived via jilter 32 and hook 3etector 34, and supplied to system controller 31.
Frill ~ultLplexer 27, a signal re~resentln~, also in recurrent sequence, the presence or absence of the low frequency signals Eros tune different low tone venerators of Tess 22, 23 and 24 is derived via filter 33, and supplied to sue controller 31.
Observe no what happens Darlene each of four possible situations prevailing at any given STY, e.g. STY 22 of Figure 3 ~30~92 One possible situation is that the telephone handset if associated with STY 22 is on-hook, and no alarm condition prevails at SUE 22. The on-hook condition is sensed at scanner 18 and the output from FISK modulator 30 is periodically supplies to that STY 22, wlllc?l response with a non-alarm output from its FISK modulator 38. This is detected by FISK demodulator I and cistern controller 31 takes no alarm action but simply continues the periodic sampling of the connection to this STY
both fox continued on-hook signal and fox continued non-alarm FISK signals.
second possible situation is that the telephone handset if is still on-hook, but an alarm condition prevails at Storage 22. The on-hook condition is still sensed at Scanner lo and the output from FISK modulator 30 is still supplied periodically to that Styli 22. However, the STY now responds with an alarm signal prom its FISK modulator 38. This is detected by FISK demodulator 29, and system controller 31 takes the appropriate alarm action, as previously described.
third situation is that the telephone handset if is off-hook, and that there is 110 alarm condition at STY 22. This off condition is now sensed at scanner 18, which thereupon does not supply output signals from FOX modulator 30 to STY 22 for the duration ox this third situation, provided the scanner 18 also senses a low tone signal received from the same syrup It will he recalled that a low tone from generator 39 is produced when no alarm condition prevails.
The fourth situation is that the telephone handset if is again off-hook, but that these is at least one alarm condition at s'rU 22. The okay condition at STY 22 is again 1.
sensed at scanner lo, but so lo the absence of the low tone signal from that same Sergei. tinder these circumstances, the scanner lo does supply output signals from FISK modulator 30 to Steele 22, of the same type as it would have supplied had the handset if been on-hook, rather than oEf-hook. This will, of koalas, cause a reply from sill 22, in the form Ox FISK modulated i 23~9:2 signals ELM its modulator I which will in turn be detected at scanner 18, and used to produce the desired alarm response.
It isle now be Lecoqni~ed that, so long as there is no alarm condition at the STUN there will be no signal in the audible range from the operation of the present invention while the associated handset is in use by the subscriber. This satisfies the subscribes desires and also complies with Regulations. On the other hand, when there is an alarm condition, these Jill be such audible signals, even when the handset is in use, in the form of the FISK modulated signals tr~vellin~ hack an forth between scanner location and subscribe premises Hovel, during alarm conditions, the presence of sicken audible signals is not only ?er~ltted by regulations, but is also affirmatively desirable from the subscriber's standpoint, since it pLovldes pronto warning to the subscriber that an alarm condition has arisen.
It will also he un-lerstoo~ that, by Nazi ox the multiplexes 25, 26 and 27 in scanner 18 (Figure 2), the same treatment which is accorded to STY 22 lo also accorded to Stun 23 and 24, in recUrLlng sequence. That is, first the scanner lo is connecter so that it intellects with STOWAGE I in the anywhere described above, then it is connected with STY 23 for the equivalent purpose, then with STY I an so EoLth in recurring sequence.
1~oreoVeL, if there are lore than three Stacy -- which will normally be the case in anal practical application -- these are all treated in Recurrent sequence in the manner described above for the single STY I
A number of a-l-litional observations about the present invention are believe to be in order artlcularly hippy cornbtnatlon ox interacting features is believed to be prevailed by retying p~imaLily upon the hLqh-ELequency en of the ~u~lble range for one alarm reporting purposes, Chile retying upon a sub-auclible signal EON
initial off; alarm LepOLtln~ purposes.

~3~g2 Use ox the hi~h-fre~llency end melees 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 zany Stylus can be acco~r~odated by the system. Use of the sub-audio end makes it possible to speak without inter-erroneous (Lillian the (presumably overwhelming) Tuna jollity of the times when no alarm is present. Yet, by shifting frown sub-audlo to huh frequency, the desired detailed information can be obtained when needed, lye. when an alarm condition arises, even Dylan oEf-hook periods It will also be noted that low tone provides redundancy for the alarm function of the system during on-hook conditions. During that condition, low tone continues to be transTnittetl from each Starr to the scanner, so long as no alarm is present at the STsJ. any low tone interruption during on-hook conditions is also sensed by the scanner, and provides what might be called a "koalas back-up alarm indication for the more 3etaile~ one ~hic`n is noL~ally provide by the FSK-~o~ulated reply Roy the syrup IloLeovQr, the allele indication during ofE-hook periods is fail-safe, since it is the dlsappeaLance of the low tone signal which indicates an alarm connation. Thus, failure of equipment in the TAO will cause a pseu~o-alaLm indication conducive to prompt collection.
In a preferred embodlrlent Ox the invention, these is one other occasion, in addition to that described above, when a particular STY has the I Inoculated sicJnal train from scannerl8 transmitted to it, even though it is not that Stacy re~lul~L Tulane in recurrent sequence That occasion is the return ELOSn of hook to on-hook status of lots associated telephone handset.
It will be recalled that the hook status is detected con each Stroll at the scanner 18. join a change from oEf-hook to on-hook status is thus detected, the Steele at that subscriber's ~L~3~9;~

premises IS preferably made the next one to receive the FSK-~odulated signal from the scanner, and therefore also the next one to provide its FISK modulated Reply. The reason for this is that only non-detalled information about the status of the instrumentalities at that location had been available during the preceding off-hook period, and it is deemed docilely to update this ~itnout delay once the off-hook condition no longer prevails.
nether 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.
Thus, all of the elements of the scanner 18 (Figure 2) may be of known form, an-l so Jay all the elements of the STOWAGE 22 (FlguLe 3).
Considering first the scanner 18, it will be recognized that the multlplexeLs 25, 26 and 27 may be of known construction. The filters 32 and 33 my be of known form, suitable for selecting the particular frequencies desired to be passed on to the hook detector 3~1 and low tone detector 35, respectively. These detectors, themselves, may also be of Nolan form, the hook detector I being a conventional part of telephone systems, and the low tone detector 35 being a detector of the presence of absence of the 25 Ho low tone signal. The TAR switch 28 may ye of known forms, and the system controller 31 may include any known circuitry capable of providing the straightforward sensing and responsive control functions which hove been described. Thus, system controller 31 may comprise a conventional source of timing signals, from which are derived the sequential operating signals for the multiplexes 25, 26 and 27. Also driven by signals derived from the timing signals may be sources, such as shift registers, of the trains of modulating signals for US
mow little 30. old gate circuitry may be used to detect the simultaneous presence of off-hook detected signals and low tone detected sigllals. Such detection is used by conventional ~%~3~36~2 circuitry to inhibit signals to the FISK ~od~llatoL 30.
Conversely, the non-detection of these simultaneous signals causes the translation Ox such signals to the US modul~toL .
Considering next the s~ru 22, the ASK demodulator 37 and the Frock modulator 38 maul again be of any known for, as also the jilter 36 which precedes the demodulator 37. The low tone geneLatoL Roy also be ox any known form capable of producing the desired 25 Liz signals when energized. The signal sources tray be simple relay circuits operated by the respective alarms, and the signal pLocessoL may be any known form of rllqi.tal logic, OX of microprocessor circuitry progLaml~eJ in conventional manner to elicit the appropriate timed signal responses, as ~Leviously described The telephone system itself is completely unaffected Al the invention. lo added filteLlnq lo Le~ul.red in the telephone Cicero in particular these is no leakage of low tone signals fryer one side of the netiloLk stitch 17 to the other because the network switch contains adequate filterincJ for other reasons, namely to isolate ~lEfeL-ellt levels of I on opposite sides of the switch.
Ryan the system ebbing the present invention lo used, not to signal an alarm, as such, but rather other states of equipment at a telephone SUI~SCLi~eL'5 premises, such as meter reaclinfJs, meteorologlc~l measurements, etc., then lo tone ran be usual to indicate that all the measuring instruments are continuing to whelk even Chile the telephone handset is ofE-hook. ruling on-hook payloads, the s1gllals Lomb any glen STY can then supply the Cole detailed data desired concelnlng tile en irk t.
Roy Seattle iltustLate-l on Flukes 1, I, end 3 can be operated in a second slay. Instead of starting the suLvelllatlce procecluLe by transll1ttinc3 tnte~Loglt~on sicJnals and LecelVlng responses, scanner 1~3 can be arLallged to sense tile presence or absellce ox the low tone slogans an only upon loss of the low tone signal Rowley a partlc~llar Sill lntelLogate that STY to -17~

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determine the Lesson fox the loss of the low tone signal. In this operating mode, the low tone signals provide the initial indications of the states of the instLumentallties. So long as the low tone septennial lo being Received by the scanner from a particular STY, the scanner does not interrogate that STY
because the presence of the low tone signal lo an indication that the STY need not be interrogated (i.e. all the instrumentalities connected to the STY ale in a "no alarm"
condition). Upon loss of the low tone signal, the scanner senses a Shinto end transmits interrelation signals to the particular STY] to determine the reason for the loss of the low tone sign]., which is indicate-1 by the response signals transmitted prom the STY
It will be understood that various modifications will occur to those skilled in the art without departing from the inventive concert, whose scope it lo desired to define only by the appended claims.

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Claims (13)

CLAIMS:

1. A system for providing communication between a central location and instrumentalities other than a conventional telephone located at the premises of telephone network subscribers, said system comprising:
means at said premises and connected to telephones in said network for transmitting to said central location a signal at a frequency below the audible range from each of said premises when the instrumentalities at the premises are in one predetermined state;
means at said premises responsive to at least one instrumentality being in another predetermined state for interrupting the transmission of said below-audible-range signal from a given premises when at least one instrumentality at said given premises changes to said another predetermined state;
means at said central location for sensing interruption of said below-audible-range signal transmitted from said given subscriber premises;
means at said central location responsive to said sensing means for transmitting interrogation signals in the audible telephone frequency range to said given subscriber premises when said sensing means sense an interruption of said below-audible-range signal transmitted from said given subscriber premises;
and means at said premises responsive to said interrogation signal for retransmitting to said central location response signals in the audible telephone frequency range and of characteristics indicative of the state of the instrumentalities at said premises.

2. The system of claim 1 wherein the interrogation signal are FSK modulated signals in the upper portion of the audible range.

3. The system of claim 2 wherein the response signals also are FSK modulated signals in the upper portion of the audible range.

4. The system of claim 3 wherein the FSK carrier frequencies are in the vicinity of 2700 and 2900 Hz.

5. The system of claim 1 wherein the below-audible-range signal is at a frequency substantially below the audible frequency range.

6. The system of claim 5 wherein the below-audible-range signal is at a frequency of approximately 25 Hz..

7. A system for signalling, through a telephone network, the condition of an instrumentality located at the premises of subscribers to said telephone network, said system comprising:
(a) a plurality of terminals connected to a plurality of telephones in said network, each terminal connected to a telephone and having:
(1) means for receiving, from an instrumentality at the premises of the telephone to which said terminal is connected, condition signals representative of the condition of said instrumentality;
(2) means responsive to said condition signals for transmitting, through said telephone network from said terminal to a central location, a low-tone signal at a frequency below the audible range when said instrumentality is in a predetermined condition and for interrupting transmission of said low-tone signal when said instru-mentality changes to a second condition;
and (3) means responsive to interrogation signals transmitted through said telephone network for transmitting, through said telephone network, response signals in the audible telephone frequency range and of characteristics indicative of the state of said instrumentality;
(b) and a scanner connected to said telephone network at said central location and having:
(1) means for sensing interruption of said low-tone signal from a terminal at a given premises;
(2) means responsive to said sensing mearns for transmitting, through said telephone network, interrogation signals in the audible telephone frequency range to said terminal at said given premises when said low-tone signal from said terminal at said given premises is interrupted; and (3) means for receiving said response signals.

8. A system according to claim 7 wherein the interrogatLon signals are FSK modulated signals in the upper portion of the audible range.

9. A system according to claim 8 wherein the response signals also are FSK modulated signals in the upper portion of the audible range.

10. A system according to claim 9 wherein the FSK
carrier frequencies are in the vicinity of 2700 and 2900 Hz.

11. A system according to claim 7 wherein the low-tone signal is at a frequency substantially below the audible frequency range.

12. A system according to claim 11 wherein the low-tone signal is at a frequency of approximately 25 Hz

13. A system for signalling, through a telephone network, the condition of one or more instrumentalities located at the premises of subcribers to said telephone network, said system comprising:
(a) a plurality of terminals connected to a plurality of telephones in said network, each terminal connected to a telephone and having:
(1) means for receiving, from one or more instrumentalities at the premises of the telephone to which said terminal is connected, condition signals representa-tive of the conditions of said instrumen-talities;
(2) means responsive to said condition signals for transmitting, through said telephone network from said terminal to a central location, a low-tone signal at a frequency below the audible range when said instrumentalities are in a predeter-mined condition and for interrupting transmission of said low-tone signal when at least one instrumentality at a given premises changes to a second condition;
and (3) means responsive to interrogation signals transmitted through said telephone network for transmitting, through said telephone network, response signals in the audible telephone frequency range and of characteristics indicative of the states of said instrumentalities at said given premises;
(b) and a scanner connected to said telephone network at said central location and having:
(1) means for sensing interruption of said low-tone signal from a terminal at a given premises;
(2) means responsive to said sensing means for transmitting, through said telephone network, interrogation signals in the audible telephone frequency range to said terminal at said given premises when said low-tone signal from said terminal at said given premises is interrupted; and (3) means for receiving said response signals.