NL192419C - System for providing signal transmission between a telephone exchange and instruments placed in the plots of telephone operators. - Google Patents

Description

1 192419

System for providing signal transmission between a telephone exchange and instruments placed in telephone subscriber lots

The invention relates to a system for providing signal transmission between central telephone network and instruments, such as alarm devices, which are placed in plots of telephone network subscribers, the system comprising: means in each plot connected to at least one telephone set of the field, for transmitting to the center a signal at a frequency below the audible range from each of the fields, when each of the instruments in the field is in a first state, which signal is sent during a recording. the off-hook condition as well as an off-hook condition of the respective telephone set; means for each field for interrupting the transmission of the signal below the audible area from a given field, when at least one instrument in the given field changes to a second state; Means in the exchange for detecting the interruption of the signal below the audible area transmitted from the given plot during both an on-hook and off-hook condition; means in the exchange responding to the detection means for transmitting an interrogation signal! in the audible telephone frequency area to the given subscriber plot; 20 and means in the field responsive to the polling signal for retransmission to the exchange of response signals in the audible telephone frequency range and with characteristics indicating the state of the instruments in the field.

A system of this kind is known from Dutch patent application 8220477. The known system makes it possible to use telephone networks to provide additional functions, in addition to those of the traditional telephone service with regard to the conversation between two subscribers. In addition, the network can be used in particular for monitoring the condition of one or more of the instruments placed in the subscriber's property.

The instruments in question may be of different types. For example, there may be a device for providing an electrical alarm signal when an irregular condition is detected in the subscriber's property. Such an irregular condition could be a fire, an unauthorized entry, a malfunction in some supervised establishment, etc. Another type of instrument may be a device that provides an electrical signal to indicate the status of some equipment in the subscriber's property, even if there is no irregularity. This can be the reading of utility meters, meteorological measurements, data to be processed from process equipment, etc.

35.

The present invention aims to provide an alternative to the known system.

To this end, the system according to the present invention is characterized in that the interrogation signal is sent to the given subscriber lot only when the detection means detect an interruption of the signal below the audible range.

The system of the present invention has the advantage that in the exchange no means are required for detecting the off-hook state of the at least one telephone in a given parcel in order to transmit signals from the power plant, such as a periodic interrogation signal, to that lot. In addition, the interrogation signal need not be output periodically, because in the system of the present invention, the transmission of the interrogation signal J0 only takes place when the signal is not present in the audible region. ----------

The invention will be explained in more detail with reference to the drawings, in which: figure 1 is a total system block diagram of an embodiment according to the invention; Figure 2 is a block diagram of a scanner forming part of the embodiment of Figure 1; and Figure 3 is a block diagram of a subscriber terminal unit (or STU) as part of the embodiment of Figure 1.

Figure 1 shows a telephone network 10 which is fully customary in all respects. Indeed, one of the features of the present invention is that it can be applied when using a conventional telephone network, without least disturbing its operation.

This network 10, which is shown in a very simplified form in figure 1, contains a number of subscriber telephone sets, respectively designated with reference numbers 11, 12 and 13. Each of these sets 192419 2 is connected to its own local telephone line. These are respectively indicated with reference numbers 14, 15 and 16. These local lines lead to a switching system 17, which is arranged in the telephone exchange. All elements of the system can take any conventional form. The telephones 11, 12, 13 may be of the dial pad or push button type. The telephone exchange 17 can be of the rotary dial, or selector rod dialer, or even of the fully electronic type. The local lines 14, 15, 16 may also be of a conventional type, including amplifiers, equalizers, etc., as needed, provided they are capable of transmitting low tone signals.

The system of Figure 1 further includes a scanner 18. This scanner is preferably located at a point where it can be easily connected to the various individual subscriber lines. This can be in the telephone exchange, where the switching system 17 is also located. In Figure 1, the fiber bonds 19, 20 and 21 are shown between the sensor 18 and the lines 14, 15 and 16, respectively. Furthermore, a separate subscriber terminal unit, abbreviated STU, is indicated at each individual subscriber location, denoted by reference numbers 22 , 23 and 24.

Attention is drawn to the fact that the equipment for only three subscribers is shown in figure 1. However, it will be clear that this is only for the simplicity of the illustration. The invention is believed to be applied to larger numbers of subscribers, in which case the telephones, connections and STUs would all increase correspondingly. This is symbolically indicated in Figure 1 by empty gaps bridged by dotted lines, between all the preceding elements of the total system.

Figure 2 shows the "interior" of the scanner 18, containing a first, a second and a third multiplexer 25, 26 and 27 respectively. These are time division multiplexers which, in a conventional manner, select signals from different connections 19, 20 and 21 at different times, and transfer the signals selected in this way to their respective outputs In addition, multiplexer 25 is a two-way device, which is also capable of selectively distributing signals at different times, to the different connections 19, 20 and 21 supplied to the other "end" of this multiplexer 25.

Thus, either end of multiplexer 25 can serve as input and output depending on the application. The multiplexer 25 is connected to a transceiver switch 28 (also shortened to T / R switch). The portion of the T / R switch 28 operating in the receive mode sequentially feeds signals from multiplexer 25 to demodulator 29 for frequency shift modulated ________________________ (30 abbreviated to FSK) signals. The portion of the T / R switch 28 operating in transmit mode receives its input signal (to transmit) from a modulator 30 for FSK signals.

Successively, demodulator 29 applies its output signals to adjusting signal controller 31, and modulator 30 receives its input signals from this controller 31.

As for the multiplexers 26 and 27, they apply their respective output signals to 35 different flters "32r33rFilter 32 applies its output signal to detector 34, while filters 33 apply its output signal to detector 35. Both detectors finally apply their output signals to the set signal controller 31.

Due to the interlocking relationship between the operation of the different elements of the sensor 18 shown in Figure 2, and the elements of each STU 22, 23 and 24 (see Figure 1), 40 is believed to be necessary to further describe in detail before discussing more fully the operation of both. For this reason, reference is now made to Figure 3, which shows the "" interior "of STU 22. It will be appreciated that all STUs may be essentially the same in build so that the description of STU 22 also applies to STUs 23 and 24. , and on all added STUs symbolized by the dotted lines between STU 23 and STU 24 in figure 1. -> "-— -» · - - 45 The STU 22 (figure 3) is connected to line 14, which is also the telephone 11 of the subscriber connects to the telephone exchange 17 and the scanner 18.

Signals received from line 14 are applied to a filter 36 within STU 22, the output of that filter is applied to a demodulator 37 for FSK signals.

Line 14 is supplied with signals from a modulator 38 for FSK signals.

50 Signals from a signal generator 39 are also applied to line 14.

Successively, the output signals of demodulator 37 are applied to the signal processing circuit 40.

The signal sources 41, 42 and 43 in Figure 3 represent electrical signal outputs from corresponding instruments (not shown) located in the same lot as the STU 22 and telefonontöè-55 set 11, and which are believed to operate under the supervision of the present system.

Signal source 41 may be, for example, a relay that closes and thereby establishes an electrical signal path whenever a fire alarm device detects an alarm condition in the subscriber's property.

3 192419

Likewise, signal source 42 may be a relay that operates in the same manner when a burglar alarm is activated, and signal source 43 may operate in the same manner in the event of interruptions in a temperature control device.

Continuing with the operating properties of the elements described above, it is necessary to first explain what is meant by a so-called "closed-loop" relationship between scanner 18 and STUs 22, 23 and 24. That is, the scanner produces signals that are sent to the STU, which responds by sending signals back to the scanner, etc., in reciprocating or closed loop relationship.

For the description of this, let us first consider the closed loop at that output of system controller 3110 connected to FSK modulator 30 (Figure 2). This system controller is informed to produce FSK-modulated signals at this output in accordance with a predetermined pattern. This pattern is such that the STUs 22, 23, 24, part of the overall system, respond to this by providing successively certain output signals to be described below. The FSK modulator 30 responds to produce an FSK modulated equivalent of the signal from controller 31. The two carrier frequencies used are preferably in the range of 2,700 and 2,900 Hz, ie, near the upper end of the frequency band normally used by a local telephone line is passed.

These FSK modulated signals from modulator 30 then pass through T / R switch 28 to multiplexer 25. Control signals from system controller 31 are also applied thereto, arranged in time with the signals from FSK modulator 30, so that the latter goes to one of connections 19, 20, 20 and 21 are routed depending on which of the STUs 22, 23 or 24 is the supposed destination of these signals from FSK modulator 30 at that time.

In case the desired destination for a given signal series is STU 22, multiplexer 25 feeds this series to connection 19, from which STU 22 is reached via telephone line 14. Note that the same signal sequence also reaches telephone 11 via line 14. More will be said about this later.

Upon reaching STU 22, and now referring to Figure 3, the above-described signal sequence is demodulated in FSK demodulator 37, after passing through filter 36, which is preferably constructed a bandpass filter for selectively passing the frequency band occupied by the two FSK carrier frequencies (e.g. the 2,700 to 2,900 Hz band). Thus, at the output of demodulator 37, the modulated signals originally provided by controller 31 (Figure 3) are reconstructed.

These reconstructed signals are supplied to signal processor 40 within STU 22.

This processor 40 is arranged to respond to the above-described signals by generating a series of modulated signals which are sequentially fed to FSK modulator 38, where they produce a corresponding series of FSK modulated signals, preferably at the same carrier frequencies as those received from scanner 18. This sequence of FSK modulated signals returns to the scanner via line 14 and link 19. In this connection it is noted that this response signal also reaches telephone 11, of course. .

At the scanner, the multiplexer 25 is activated by controller 31 temporally coordinated with the expected arrival of this response signal sequence from STU 22 to pass signals on ___ link 19 to the FSK demodulator 29, via the receive portion of T / R-. switch 28. The demodulator 29 restores the signals used for modulation of the FSK signals in the STU 22 and applies them to system controller 31.

Returning now to STU 22 (Figure 3), it is noted that the modulated signals produced by signal processor 40 provide information about the state of the signal sources 41, 42 and 43.

For example, if in STU 22 there are no closed relays that indicate an alarm state of the various instruments under supervision, then processor 40 will feed a predetermined pattern "of ------—— - modulated signals produced When one or more closed relays are present, correspondingly different patterns are produced, and the demodulated signals which finally reach the controller 31 of STU 22. Also, the system controller 31 responds to the individual received signal patterns on a For example, when a signal-50 pattern is received indicating that there is an alarm condition in signal source 41 of STU 22 (Figure 3), the system controller 31 provides a corresponding alarm signal to an indicator, which may be an indicator in the fire station under the care of which the plot of the subscriber is in which the STU 22 is installed. fitting of the signal pattern received by each STU is common per se and may take any form. Therefore, the means for accomplishing these applications are not further described or shown herein.

Attention is now being re-focused on the previously noted fact that the FSK signals moving back and forth between scanner 18 and a particular STU also reach the telephone with this STU

192419 4 belongs. This is not a problem as long as the telephone is free, because these FSK signals go unnoticed by the subscriber during such a free state. Not so during a busy state. The FSK signals are within the audible frequency range. They are therefore heard by the subscriber when he tries to use the telephone for normal conversation purposes. This is quite disturbing, in particular because these FSK signals are intended to be repeated at frequent intervals, in order to provide relatively current indications of the condition of the devices under supervision.

Even if the audible effect of these FSK signals were to be considered acceptable by the subscriber, in many cases they would still run counter to telephone company and / or government regulations, which occupy the introduction of such strange audible signals into the network during- Prohibit 10 states.

This issue is resolved as follows.

The generator 39 present in each STU (Figure 3) is arranged to produce a signal at a frequency significantly below the audible frequency range. For example, this generator 39 may be capable of producing a signal at a frequency of approximately 25 Hz. Because of its operation at such a low frequency, generator 39 is referred to as a "low-tone" generator.

The generator 39 does not operate continuously. But it is controlled by signal processor 40 to be in one or the other of two positions. As 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 then reaches the sensor 18 via telephone line 14 and link 19. When one or more of the signal sources 41, 42 or 43 is in an alarm state, signal processor 40 causes the low tone generator 39 to stop supplying the low frequency output signal. This low-frequency signal then no longer reaches scanner 18. As previously indicated, each STU is equipped essentially in the same way as the STU 22 shown specifically in Figure 3, and operates essentially in the same manner.

In the scanner 18, the multiplexers 26 and 27 are controlled by system controller 31 to successively sample the signals appearing at connections 19, 20 and 21, respectively.

From multiplexer 26, a signal representing the hook state of the various telephones 11, 12 and 13 in a periodic order is derived through filter 32 and hook detector 34 and applied to system controller 31.

From multiplexer 27, a signal, which also represents in a periodic order 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 fed to system controller 31.

It will now be considered what happens during each of the four possible prevailing situations. To each STU given, for example STU 22 in Figure 3.

A possible situation is that the telephone 11 connected to STU 22 is free and no alarm condition is present STU 22v t> e free state is detected by sensor 18 and the output signal of ------------- FSK modulator 30 is periodically supplied to that STU 22 which responds with a non-alarm output signal from its FSK modulator 38. This is detected by FSK demodulator 29 and system controller 31 does not take an alarm action, but simply continues the periodic chime. I IWISWIII HJ from the connection to STU 22, both for the continuous free signal and for the continuous 40 non-alarm FSK signals.

A second possible situation is that the telephone 11 is still free, but there is an alarm state at STU 22. The free state is still detected on scanner 18 and the output of FSK modulator 30 is still periodically supplied to STU 22. However, the STU -------- is now responding with an alert from its FSK modulator 38. This is detected by-FSKdanariuiaiaft --- - 45 29 and system controller 31 takes the appropriate alarm action, as previously described.

A third situation is that the telephone 11 is busy and that there is no alarm condition at STU 22.

This busy state is now detected on scanner 18, which does not supply any output signals from FSK modulator 30 to STU 22 during this third situation, provided that the scanner 18 also detects a low-tone signal received from the STU 22. remembered that 50 a low tone is produced by generator 30 when there is no alarm condition.

The fourth situation is that the telephone 11 is busy again, but there is at least one alarm condition on STU 22. The busy state on STU 22 is redetected on scanner 18, but also the absence of the low-tone signal from STU 22. Under these conditions, scanner 18 feeds output signals from FSK modulator 30 to STU 22, of the same type as that added. when the telephone 11 would be free, rather than busy. This, of course, will cause a response from STU 22, in the form of an FSK modulated signal from its modulator 38, which is sequentially detected at scanner 18 and used to produce the desired alarm response.

It can now be noted that, as long as there is no alarm condition at the STU, there will be no signal in the audible range while the associated telephone is being used by the subscriber. This meets the wishes of the subscriber and also complies with the regulations. Otherwise, when there is an alarm condition, there will be such audible signals, even when the telephone is in use, in the form of the FSK modulated signals going back and forth between the location of the sensor and the plot of the subscriber. However, during alarm conditions, the presence of such audible signals is not only permitted by the regulations, but is also considered desirable from the subscriber's point of view, as this provides an immediate warning to the subscriber that an alarm condition has occurred.

It will also be appreciated that, through the multiplexers 25, 26 and 27 in scanner 18 (Figure 2), the same treatment given to STU 22 is also given to STUs 23 and 24 in repeated order, i.e. first, scanner 18 is connected such that it and STU 22 interact with each other in the manner described above; then the scanner is connected to STU 23 15 for the same purpose, then to STU 24 and so on, in a periodic order.

In addition, when there are more than three STUs - which will normally be the case - they will all be repeated in the order described above for the single STU 22.

A particular "happy" combination of interactions is obtained by relying on the high-frequency end of the audible range for alarm-mode purposes in the off-state 20 and on a sub-audible signal for first alarm-mode purposes in the busy state.

The use of the high-frequency end allows for a relatively high data rate, which means that relatively detailed information about the devices under supervision can be obtained, and also that this can be repeated regularly, and that relatively many STUs can be included in the system. Use of the sub-audio end allows speaking without interference during the (presumably overwhelming) most of the time when no alarm is present. However, by shifting from sub-audio to high-frequency, the necessary detailed information can be obtained if necessary, i.e. when an alarm condition occurs even during busy periods.

It is also noted that the low tone provides redundancy for the alarm function of the system during idle states. During this state, the low tone is continuously sent from each STU 30 to the scanner, as long as no alarm is present at the STU. Any interruption of the low tone during free states is also detected by the scanner and provides what may be termed a "coarse" support alarm indication for the more detailed indication normally provided by the STU's FSK modulated response.

In addition, the alarm indication is resistant to disturbances during busy periods because it is the disappearance of the low-tone signal indicating an alarm condition. Equipment failure in the system. In a special embodiment of the system, in another case, except for the one described above, --- where a particular STU is sent the FSK modulated signal array from probe 18, even__ when this STU is in it is not normally the turn of the periodic order.

40 This case is the return of the busy to the free status of the associated telephone.

It is recalled that the hook status is detected for each STU in the scanner 18. Thus, when a change from busy to free status is detected, the STU in that subscriber's plot is preferably the next one that uses the FSK modulated signal from the subscriber. scanner and therefore the next one that provides its FSK modulated response. This is because only —45 detailed information about the status of existing devices has been available in that location during ------- the previous busy period and it is considered desirable to update them without delay once the busy status no longer exists. .

Another important feature of the described system is that the individual components of the total system can take a number of known embodiments.

Thus, all the elements of the scanner 18 (Figure 2) can be of a known shape, as can the elements of the STU 22 (Figure 3).

When first considering the scanner 18, it will be apparent that the multiplexers 25, 26 and 27 may be of a known construction. Filters 32 and 33 may be of a known form suitable for selecting the individual frequencies to be passed to hook detector 55 34 and low tone detector 35, respectively. These detectors themselves may also be of known form; the hook detector 34 is a common part of telephone systems and the low tone detector 35 is a detector for the presence or absence of the 25 Hz low tone signal. The T / R switch 28 may be of a known form and the

Claims (2)

192419 6 system controller 31 may include any known circuit capable of providing the direct scan and response control functions described. The system controller 31 may therefore contain a conventional clock signal source from which the successive control signals for the multiplexers 25, 26 and 27 are derived. Also, driven by signals derived from the clock signals, there may be sources, such as shift registers, for the array of modulated signals for FSK modulator 30. AND gate circuits can be used to detect the simultaneous presence of busy detection signals and low-tone detection signals. Such detection is used in conventional circuitry to suppress signals to the FSK modulator 30. Conversely, not detecting these simultaneous signals causes the transmission of such signals to the FSK modulator. 10 Next, consider the STU 22, the FSK demodulator 37 and the FSK modulator 38. These can again be of a known form, as can the filter 36 that precedes the demodulator 37. The low tone generator can also be of any known form which, when energized, is capable of producing the desired 25 Hz signal. 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 a microprocessor circuit programmed in conventional manner to obtain the appropriate clock signal responses, as previously described. The telephone set zetf is not affected at all by the described signal transmission between the subscriber terminal units and the exchange. No additional filters are required in the telephone set; in particular, there is no crosstalk of low-tone signals from one side of the switching system 17 to the other, because the switching system contains suitable filtering for other reasons, namely to separate different DC voltage levels on opposite sides of the switching system. When the described system is used, not for signaling an alarm as such, but rather for signaling other states of devices in the telephone subscriber's field, such as meter reading, meteorological measurements, etc., the low tone can be used for indicating that all measuring instruments are continuously operating even when the telephone set is busy. During free periods, the signals from each STU can then provide the desired more detailed data regarding the devices. Thus far, the system known from Dutch patent application 8220477 has been described. The invention relates to a modification thereof, in which instead of starting the monitoring procedure by sending interrogation signals and receiving responses, the sensor 18 detects the presence or absence of the low-tone signals and only when the low-tone signal of a particular STU is lost, it is queried to determine the reason for the loss of the low-tone signal. Here, the low-tone signals provide the first indication of the condition of the instruments . As long as the low-tone signal is received by the sensor of a separate STU, the sensor does not ask -35 · · STU because the tone signal's ononwoaghoid is our indication dot do STU ... need to be connected {cLwJL-all connected np Hn style in rmn 'nint nlnim ”tn - absence of the low-tone signal, the scanner detects a change and sends interrogation signals to the appropriate STU to determine the reason for the absence of the low-tone signal, which is indicated by the response signal sent by the STU. 40 System for providing signal transmission between 45 instruments, such as alarm devices, which are arranged in telephone network subscriber units, including means in each parcel, connected to at least one telephone network operator. one telephone set of the field, for transmitting to the exchange a signal at a frequency below the audible range from each of the fields, when each of the instruments in the field is in a first state, 50 which signal is sent during a on-hook condition as well as an off-hook condition of the respective telephone set; means in each field for interrupting the transmission of the signal below the audible area from a given field when at least one instrument in the given field changes to a second state; 55 means in the exchange for detecting the interruption of the signal below the audible area transmitted from the given plot during both an on-hook and off-hook condition; 192419 means in the exchange responding to the detection means for transmitting a polling signal in the audible telephone frequency area to the given subscriber lot; and means in the field responsive to the polling signal for retransmission to the exchange of response signals in the audible telephone frequency range and having characteristics indicating the state of the 5 instruments in the plot, characterized in that the polling signal is sent to the given subscriber- plot only then, when the detection means detect an interruption of the signal below the audible range. Hereby 3 sheets drawing ...... * ...... _ ___ ... ίιΐΛSSMÏ * «4 * 1„ mi, · - **** .. ... Itftlll -